It's really hard to learn to travel alone, but I've always seen it as: if you can't enjoy traveling by yourself, how will you really enjoy it with others? I think travel can be a shared experience, but I tend to think of it as separate individual experiences being simultaneously shared. That way I can get there, and if I want to do something my friend doesn't, then I will, and s/he can do whatever s/he wants, and then we can meet up later and share.
The downside of traveling with friends always comes in deciding what to do and passive-aggression (no, we can do whatever you want, I don't care, it's okay) and all that. Learning to travel alone was the best thing I could have done to escape that 🙂
I'd recommend Europe for a first time international traveler. It's generally safer than the US, and everyone tends to have a high level of English, making the learning experience relatively harmless. Japan is also a good one, but it's sooooo expensive, and the English level isn't very high. If you know a native, or have a friend who lives there, though, it can be really amazing. But, if you're learning to travel alone, that can be a good thing - figuring out your way around with signs you can't read, etc., has its own fun to it 🙂
I wish I knew the languages, though :/