The accusation is not new. In the early 1970s the United States accused the old European Monetary System (EMS) of keeping the currencies adhering to it artificially high.
Inter alia, the EMS - with fixed exchange rates but with predefined fluctuations within it - was the European response to the US-prompted end of the 1944 Bretton Woods agreement.
Nevertheless, it was also Europe’s reaction to the planned weakness of the dollar during Jimmy Carter’s Presidency, when precisely the dollar area sent huge capital flows into Germany, which had a "high" Mark, thus pressing it against the French Franc and hence destabilizing the entire European internal monetary exchange system.
Furthermore, in the early 1980s, the British Labour Prime Minister, Denis Healey, got convinced that the EMS was a real German "racket", considering that the German Finance Minister had told him that his country planned to have a comparative advantage precisely by limiting the depreciation of the other European currencies.
This happened because Germany had lower labour cost-driven inflation rates and, hence, a currency with fixed rates would have anyway ensured export-driven surpluses only to Germany.
However also the G20 long negotiations have never led to any result: currently, in absolute terms, the German export-led surplus is much larger than China’s, namely 8.6% of the German GDP.
In fact, according to IMF estimates, the surplus is equal to 271 billion US dollars, a huge sum capable of changing all global trade flows.
Finally Chancellor Angela Merkel replied to Trump (and to Navarro) by recalling that the European Central Bank is the institution issuing the euro, but it is not lender of last resort. Nevertheless, she has not contradicted the US President about the fact that the Euro is really undervalued.
Furthermore, when we look at the currencies undervalued as against the US Dollar, we realize that the most undervalued currency is the Turkish Lira, followed by the Mexican Peso, the Polish Zloty, the Hungarian Forint, the South Korean Won and, finally, our own Euro.
Finally, when we look at the number and size of transactions denominated in euros, the European currency is already the second most traded currency in the world.
Hence, probably the undervaluation of the Euro against the US Dollar originates more from the expansionist policy of the European central Bank than from Germany’s actions for its exports and monetary parities.
Certainly Germany gains in having a currency that is much weaker than it would be if it were only a German currency but, on the other hand, with a Euro artfully devalued, the “weakest” Eurozone countries succeed in having lower interest rates than they could obtain with their old or new national currencies.
Moreover, it is worth recalling that Germany exports profitably both in countries where the currency is stronger than the Euro and in regions where the currency is even more depreciated as against the US Dollar, such as Japan.
According to last year’s data, the United States have a trade deficit with Germany equal to 60 billion US dollars.
Germany exports mainly cars, which account for 22% of their total exports to the United States.
It also exports - in decreasing order - machine tools, in direct competition with Italy, electronics, pharmaceuticals, medical technologies, plastics, aircraft and avionics, oil, iron and steel, as well as organic chemicals. All German exports are worth 35% of its GDP.
Why, however, is the Euro depreciated because of Germany?
Firstly, since 2000 the German cost of labour has grown by 20-30% less than in the Eurozone’s German competitors.
Hence German products were ipso facto 20% more competitive than those of the others, without any exchange rate manipulation.
If Germany still had had the Mark, it would have automatically appreciated by 20%.
The appreciation of this hypothetical Mark would have changed demand, by reducing exports and increasing imports by the same percentage.
In that case, the ideal would have been a floating exchange rate - and this should also be the case for a re-modulated Euro compared to the current situation.
A fluctuation prefiguring the creation of a new monetary "basket" with the major currencies, with exchange rates floating within a certain range, but much more realistic than the current ones.
A further cause of the current account surplus in Germany is the intrinsic strength of its exports - hence Germany does not suffer the competition of low-tech economies, such as Italy’s.
Another reason for the excessive German surplus is the low domestic demand, with the relative increase in private savings.
An additional cause of the surplus is the fact that savings have long been higher than investment.
In 2015, German savings amounted to 25% of the Gross Domestic Product (GDP), while investment was worth only 16% of the GDP.
Obviously, another decisive reason for the accumulation of such a large German surplus was the fall in oil prices.
Therefore, the vast German surplus and the Euro undervaluation foster its exports, but block the exports of the other Eurozone countries.
In fact, according to our calculations, if Germany stimulated its domestic demand, thus allowing its inflation to increase, this would be enough for the final stimulus of global demand and, above all, it would make the Eurozone economies under crisis get out of their predicament.
Hence the real problem of too high a Euro is not so much for the United States, which can devalue as against the Euro whenever they want and anyway have still their own autonomous monetary policy, but rather for the single currency countries in the Mediterranean, which are experiencing a downturn caused by too low domestic demand.
Could we also do as Germany? No, we could not.
It is not possible for anyone in the Eurozone to create an 8% surplus, such as Germany, and not all countries could benefit from a devalued exchange rate of the European currency.
As many politicians say, restructuring the production system to increase productivity means - in a nutshell - years of deflation and high unemployment, which create a negative multiplier effect.
We cannot afford so - the social and economic conditions have already reached the breaking point.
Hence, let us put our minds at rest, the ''two-speed Europe" will last generations and it would be better if this could also be reflected in the single currency.
Or better in a series of two-three currencies deriving from the Euro with pre-fixed exchange rates floating within a range.
Furthermore, Germany will certainly replace China as the "bad" currency manipulator and there will be increasing competition between it and the rest of Europe.
Therefore, the German export surplus actually leads to an unfair competitive advantage over the Eurozone countries and, in other respects, over the North American exports.
This is the sense of the struggle against the Euro waged by President Trump and his future Ambassador to the EU, Ted Malloch, who has stated that the Euro may "collapse" over the next eighteen months.
The Euro is certainly undervalued.
According to a study carried out by Deutsche Bank, the Euro is allegedly the most undervalued currency in the world, according to the criteria of the Fundamental Equilibrium Exchange Rates (FEER).
And the Euro is undervalued even if we look at its external value and the mass of transactions of the individual countries currently adopting it.
Hence, not only can Germany be accused of managing an improper comparative advantage over the dollar and the other major currencies but, according to the FEER data, the accusation holds true even for Italy and for the other single currency European countries.
With a view to solving the issue, some analysts - especially North Americans - think it should be Germany to leave the Euro.
On the one hand, Germany cannot revalue its currency (which is also a political problem – suffice to think of German savers) without the Euro appreciating also for the Eurozone weak economies, such Italy and Spain.
The World Bank believes that the German trade surplus is at least 5% too high and, hence, the German exchange rate is largely undervalued by at least 15%.
In fact, the differential between the German Euro and the Euro of the Eurozone weakest countries is 20%.
This means that, in terms of Purchasing Power Parity (PPP), the Italian or Greek Euro is worth 20% less than the German one.
The issue could be solved with an equivalent 20% Euro revaluation, combined with an expansionary fiscal policy.
However, this cannot be done as long as Germany is within the Euro. This means that Germany cannot revalue the exchange rate without doing the same in the other 17 countries that adopt the European single currency.
This would mean definitively destroying the Italian, Greek, Portuguese and Spanish economies.
Therefore, if Germany came out of the Euro, its new currency would appreciate as against the non-German Euro and the other countries would have a devalued currency, which could help them in exports.
There are two ways in which the German trade surplus creates deflation - and hence crisis - in the rest of the Eurozone.
Obviously the first is by pushing up the value of the European currency.
A strong euro weakens the demand for European exports, especially for the most price-sensitive goods of the Eurozone Mediterranean economies.
Moreover, the high value of the European currency reduces the price of imported goods, thus negatively reinforcing the price fall - another deflationary mechanism.
And the German inflation which, as everyone knows, is lower than in the other Eurozone countries, further weakens the peripheral economies.
Hence a landscape marked by low domestic demand and national markets’ production crisis.
However, in Navarro’s and in Trump’s minds, there is the implicit belief that trade imbalances can be solved in a context of free-floating currencies.
It is not always so and, however, fluctuations apply only when there are structural changes in trade systems - in principle all players envisage and operate, for sufficient time, with fixed or maybe slightly floating rates.
Therefore, reading between the lines, what both Trump and Navarro really tell us is that the very Euro membership is an act of monetary manipulation.
Hence, what is done?
The unity of the European economy is broken, with unpredictable effects and further global chaos, while the United States acquire exports that were previously denominated in euros.
Or the United States could impose quotas or specific tariffs for Germany, which is illegal in WTO terms but, above all, would expose the United States to a series of reprisals and retaliation by Germany and probably also by the rest of the Eurozone.
There is no way out: therefore, again reading between the lines, probably Trump is telling to the Eurozone weak economies that they should leave the single currency, which is only in Germany’s interest, and create new post-Euro currencies, which will be somehow pegged to the US Dollar.
Or Trump and Navarro could define a new relationship between Euro, Dollar, Yuan, Ruble, Yen and some other primary currencies on the markets and impose a predetermined fluctuation between them, but obviously the Euro would enter this new "Bretton Woods" by being valued in line with the markets and not being overvalued as today.
Europe, however, shall put back in line and tackle all trade and political issues with Trump’s America, which will make no concession to anyone and, most importantly, does no longer want to favour Europe militarily, strategically, financially and commercially.
In particular, Donald J. Trump has in mind the big game with Russia and China. He is scarcely interested in a continent, such as Europe, which is not capable of defending itself on its own and shows severe signs of structural crisis.