Which European country which has never been in a war against the US has the highest GDP?

[buritobr]

Answer: Poland, European 7th biggest GDP

The European 6 biggest economies had already been in war against the US
1st Germany: was in the war against the US in the WW1 (1917-1918) and WW2 (1941-1945)
2nd Russia: US army took part in the Russian Civil War in 1918 and fought against the Red Army
3rd France: revolutionary America and revolutionary France fought against each other in 1798-1800
4th UK: Revolutionary War (1775-1783) and War of 1812-1815
5th Italy: WW2 (1941-1943)
6th Spain: Spanish American War (1898)

List of countries by GDP https://en.wikipedia.org/wiki/List_of_countries_by_GDP_(PPP)

[True Federalist (진정한 연방 주의자)]

You forgot the Regency Kingdom of Poland (1917-18) that was a German puppet state. While its troops never directly confronted U.S. troops as far as I know, it was at war with the Entente during the period that the U.S. was in the Great War. Next on the GDP list is the Netherlands.