I don't think it was ever taboo in the US, but I've noticed that older people are much less accepting of it.
I have lived in most areas of the USA, I say that having a shaved head is not common but again it is not uncommon as I see a few guys with that appearance every time I am in a store. All ages but more middle age or older. However I do see young guys. I first shaved my head in !980 when it was quite uncommon. Accepted after some teasing.