As always, these things can't be generalised. Every country has people that talk about their own problems, and every country has "patriots" that will deny anything is happening. There are just a lot of Americans on the internet, so people notice those who relentlessly praise America more.

After all, few countries literally ingrain "[country] exceptionalism" into their population in their school system. Many Americans, while thinking they are pointing out problems, still say "but it's still better than almost any other country at X".