Uh, in fact, British and American natives are the worst, when it comes to homophonic errors. Your/you're, its/it's, their/there/they're - unless they're well educated (and often even if they are), chances are that the natives will get them wrong whereas foreigners won't. That's because they think of the language in terms of sounds first (as they learnt it before they could read), whereas foreigners are forced to think about it in logical terms first.