Oh, I see where you got confused. When people say 'Americans do something' they mean 'most Americans do it' or 'significant portion of American population do it', not 'all Americans do it'. You see, countries are big and there are a lot of people in them and it very rare for everyone in a country to think exactly the same. That's why we usually focus on the prevailing attitudes that shape the country over the years instead of looking for believes shared by ALL citizens (because they don't exists). Currently over 40% of Americans believe that "God has granted America a special role in human history" and it was way higher in the not so distant past, that's why someone could say that "Americans believe it". Hope this helps.
"Some Americans believe this, therefore the Americans who don't and are actually trying to fix this Godforsaken country, and get upset when people accuse them of believing it, are hypocrites and crybabies who can't take criticism."
I know how you feel but you have to understand that the memes are not about you personally. We know that most Americans on lemmy are the cool ones. The ones that don't have guns and are not afraid of socialism. The memes are about the other Americans and, you know, we're just joshing. I though that's obvious, that's why I asked why everyone is suddenly so touchy about it. Usually the cool Americans are in on the joke. Now they are all sensitive about it. It's just weird.