I was in a trans-Atlantic relationship for a couple of years (although all told we spend a year's worth of time physically together through visits). So I really feel your pain, especially since he apparently is not as interested as you are.
All I could recommend is to keep in touch, but don't get your hopes up, and don't make it too obvious how deeply you feel for him. Keep your eyes open for other people (although I know it can seem like there's no one in this country you'd waste your time on), and try to keep moving forward with your own life.
Best case scenario - he suddenly realises you're the one and is ready to meet you halfway. Worst case: he finds love in the US, totally moves on and you're left hanging. Is it worth the risk? I think you probably already know!
Good luck!