Native English speakers when trying to speak Portuguese find it hard to speak A with tilde (~). Like when they say "São Paulo" they say "Sao Paulo". Ã is the nasal A, which sounds like the U in "sun" and "burn", while the standard A sounds the same as in "car".
I don't know why this happens, since the phoneme exists in English...
I don't know why this happens, since the phoneme exists in English...