Why do Mexicans pronounce v's as b's?

Answer 1

Both v and b are pronounced the same in Spanish, as a bilabial fricative. Neither one sounds exactly like an English b, which is a bilabial plosive, but the Spanish v sounds more like a b to English speakers than it sounds like a v. It also looks like a b when Spanish speakers pronounce a v or a b, because in a bilabial fricative the lips appear to touch, whereas the English v is a labio-dental fricative produced by placing the teeth on the lower lip.