Quite contrary, majority believes US falls back behind on almost everything (as it should be statistically).
But I belive the original snark, and explanation, wete referring to the majority of people living inside the US. From that perspective there's an implicit understanding that the US leads the way (in every field) and their approach to society is best (in all contexts.)
This is of course evidenced by the number of people who desire to live there, and hence the immigration issues. (Immigration issues being a uniquely US phenomenon.)
I live in US. I keep hearing stories how everything is better in Europe (they tend to cherry-pick good stories from different EU countries). The only areas where we get a consensus that US leads the way are probably gun rights and large pickup-trucks.