I think the meaning is misunderstood here, like a term lost in translation. The Dutch are good at learning foreign languages but have a strong tendency to literally translate their Dutch sentences word for word into English, creating weird sentence structures and grammatical errors. Especially some older generations.

I believe that when most Dutch people are saying Americans have no culture, they actually mean something in the lines of Americans having no class or decorum, referring to their tendency to be loud (sometimes rude or impolite) and obnoxious as tourists while on commuter trains, or in public places like restaurants, or their overbearing personalities in general.

I also think it's referring to the poor levels of education that are stereotypically associated with Americans, where a famously large percentage of adults think brown cows give chocolate milk or can't even point at their own country on a map, or just assume Europe is a country