Mostly Europeans amuse themselves about how Americans think they're living in a first world country while having absolute basic developed-world-shit just flat out fail. I.e. health care, consumer regulation, public transit, education, clean water. Sure the US is not uniform but it's a single country. Even Europe has it's own problems but most countries have this stuff figured out more or less.
The reason Europeans mock Americans is because Americans always ALWAYS complain about how they're getting fucked. And Europeans are just like "lol that shit ain't an issue here". Which a) contributes to Europeans thinking the US is a shithole and b) making Americans seem kinda whiny.