They are virtually the same. 'Friend' is much more common in the U.S.

buddy and friend are almost the same, though I wouldn't use "buddy" for someone I don't know very well. "Friend' is for someone you know pretty well. "Buddy" is almost slang.

Guys use the term buddy more, like they might use the phrase best buds instead of best friends. A girl could call a guy her buddy and that would imply a brotherly relationship. Buddy and bro (short for brother) are used pretty similarly in casual speech. Buddy is also used more when speaking to someone directly. For instance, whats up buddy would be a more natural greeting than whats up friend. I think buddy tends to denote a more close or distinct relationship than friend but its fairly casual word.

I think where I'm from at least buddy is only really used when an older person greets a young person. And I think it also implies a close relationship. But I never really hear friend in greetings like "hey friend". Mate is probably more common in Australia =)

All 3 are correct in their comments but I would go further and say that in the USA buddies would be a good friend more for a man than a woman. I have never come across a woman using that expression.