I feel the same way.
Me and my girlfriend are different ethnicities, and families whom are completely different in terms of cultural and social backgrounds.
I realise after 3 years of being together there is very little chance of us getting married, the family would worse disown her, or at the very least despise her, my family would frown upon it also.
We are going different uni's, and our differences are now most obvious to me. It saddens me to think she would be happier with a bf of the same ethnicity, since they have so much in common in terms of religion, traditions and social background.
For me a long distance relationship only makes our future very bleak, since she would eventually realise the differences I already feel at this moment.
But I you have to remember that our experiences shape who we are, and I will see how long this relationship will last before it falters - like it is now for me.