Yes, the reason Euro bands "dumb down" setlists on US tours is because American audiences are dumb. Has nothing to do with them touring in Europe 10x more and crowds having more of a chance to catch their favorite bands and hearing their favorite songs.
Bands play 'staple' sets in America because they don't tour here often, so they try to play the songs most people want to hear. It'd be cool to hear some deep cuts. Don't expect it.