It’s not so common in the states to use “if I was you” to begin with, you said you were mean when you use English, but it looks like you’re mean when you use Cantonese, that’s your character, not your language style.
It appears to me you don’t like to be questioned, that’s fine, we’re all defensive when others question us, but in your example, it’s not even the question of frequency of usage, it’s fundamentally incorrect to use it…
Unlike you, I know shit about English, I’ve never learnt English to begin with, my years in school taught me nothing of English. I know how to speak simply listening to TVs, that’s about my god damn English level. Hell if I need the urge to be a grammar Nazi, I’ll pick someone who’s even worse than you as a 2 decades citizen in the states, at least that’ll give me more thrills and satisfaction seeing people got beaten down and can’t defend for themselves, isn’t that’s the whole point of being a Nazi to begin with?