Why is that on the internet, people assume you're a male from America, but if you're a vegan on the internet, people assume you're female?

My guess would be that with the huge amount of American males (it is a big country after all) people just assume. And women are known to care about animals more, whether that is true or not.

I've been called a guy before and my name doesn't exactly strike people as male. I am female. I've been on the internet long enough not to care.