I think it's because the politics stream only has americans anyway

Naw… I've seen a few of our friends from across the pond in the UK, our frost-bitten cousins to the North in Canada and even one guy from Brazil. Just gotta dig a bit.

Nobody is stopping anyone from posting about politics form the rest of the world. Just be sure to put in some kind of context/explanation so people will know what you're talking about.

title

It is only perceived this way because most followers of this stream are Americans. But this doesn't prevent anyone from submitting memes dealing with other politics.

this is what I said in the title

I'm pretty sure that upwards of half of the imgflip politics stream are absolutely NOT American at all, even though they try desperately to influence US politics by pretending they're conservative.