I'm American and even I know the stereotype you speak of.

I don't think what you said was racist, but you are speaking to a bunch of kids and Brits, and from my personal experience, it's downvote city in sub-reddits where they are the majority population. They don't listen to reason or allow explanations.

Most of them will look at my comment to you and subconsciously judge me in a sterotype because I'm American lol.

Perhaps next time just say, "a stereotype I have often found true is..." or "most Albanians I know all fit the stereotype of loyal but extremely hot-headed."

I bet you, this situation could have been about Irish or red-heads and their flashes of anger, a stereotype known the world around, and you would have been downvoted.