It's just a joke. But I didn't upvote it because it's an old, worn-out, recycled joke by this point.
There's a lot of people in the United States. This country is huge, and states can differ widely in culture, climate, and ideology (e.g. compare Florida to Colorado, or Texas to California). But unfortunately, you don't see that diversity on the internet. Especially websites like Reddit, where the majority are internet-cultured white male teenagers and 20-somethings...who for some reason upvote this joke over and over again. Maybe it's because they are pretty young and it's still a new joke to them (I don't mean that as an insult). But maybe it's being upvoted by Americans who see this as self-deprecating humor? After all, everything in this gif is a parody of American stereotypes.
I can imagine how foreigners would gather a negative view of Americans because of it. Though I think it is misplaced, because they take posts like this seriously and don't at least consider that it might just be us making fun of ourselves. Or they don't consider that they might be looking at the opinions and humor of a relatively homogenous group of people that don't actually represent the views of their entire country.
Still, the reaction that posts like these get from non-Americans tends to have equally obnoxious and malicious (as opposed to humorous) stereotyping of Americans as loud, dumb, and obese rednecks. Probably because these reactions are also coming from similar homogenous groups in other countries.
I don't think there's much of a difference between the "AMERICA FUCK YEAH" people and the "AMERICA SUCKS BALLS" people. Just a bunch of opinionated and brash young dudes from different countries.
So yeah, I guess I just wanted to emphasize that the USA and other countries are heterogenous groups of people and Reddit's vocal majority is relatively homogenous. So take all of the pro-America and anti-America drivel on here with a grain of salt. It doesn't represent my views as an American, and it certainly doesn't represent my country as a whole.