the biggest one seems to be culture.
In today's world it seems this factor is in a patch of an evolutionary change. Cultures are coming closer with the aide of technology and media and globalization, etc - the line is blurring. Just remember that any relationship can survive when both the parties are ready to make some adjustments in their lives for each other. If you cannot even do this much (or him) then probably the relationship wont last. And for such people, which relationship really ever lasts?
still open question whether his parents will accept me...
Why will they not? All parents really worry is their son/daughter's stability in their decisions. My mother was very skeptical about my marriage (I am Polish, she is not). But eventually we did convince. You need to be aware of his parents and be respectful in a natural way. Is it something very big? Just be respectful, and polite. You are a girl who their son have loved, this alone is not insignificant for any parent.
If they are aggressive parents, no girl (even from their own country) will ever be happy with them.
Very less is changed in today's world when two people are from different countries. Other than perception and past values which we often wonder whether applicable even today (and they are not), most things are similar.
If he loves you and you love him ... remember that being aware of each other, adjusting for each other, sharing with each other is something that will last for an entire lifetime. Not always you two might thing of a thing in the same way, sometimes anger can come. But any relationship to be successful, you need to manage it in a manner which keeps LOVE intact at the top of all. This is very much possible for two people who decide to do so, and are honest with each other in their commitment and dedication.