I always think of “bro” as being a hyper version of “dude.” It’s generically applied to any random person, but it’s also exclusively male. So using it implies “this ingroup is assumed to be 100% male.”

On the other hand, I’ve seen and heard “dude” and “guy” used by and applied to women by other women. Not common but it happens. But I’ve never heard “bro” used that way.