> Germany was behind the UK even before WW2.

Yep. -- I noticed that the first link of my comment is somehow not working. Here is another reference for those who want some numbers. It is a German publication ("Deutschland in Daten", PDF) but the relevant tables should be understandable anyway:

https://www.bpb.de/system/files/dokument_pdf/deutschland_in_...

For GDP per capita in "International dollar"/"Geary-Khamis-Dollar" for Germany, France, Italy, Japan, Great Britain, USA in the period 1850-2019, see p. 312 and 313.

According to this publication, 1930, 1940 and 1950 the German GDP per capita was about 75% of that of Great Britain. However, there was a big dip right after 1945 shown in the second table.

The German "economic miracle" ("Wirtschaftswunder") of the 1950s and 1960s was in essence not an outperformance of other western countries in absolute terms, but a catching-up process with them. The same holds for Japan. The process lost momentum, when parity with most of the other major economies was reached.

However, the USA have always been considerably ahead since WW2. -- So much to the slogan "Make America great again". It seems to be based on a very distorted self-image of having a backward economy, for which I have no sound explanation as an outside observer. And even if it were not about the general economic situation, but about a growing disparity inside the country, then a solution to better the situation, when the country is already so much ahead economically, cannot come from outside, but must be domestic.