oooh. Now I get it. Relatives will obviusly talk. How is it like having a Gora son in law? Why Gora etc etc.... Then someone else will do something else and your DD's marriage won't be the latest gossip anymore. They will forget about her and include you in the "this one's daughter did this" gossip. Have fun. Don't think too much. If someone asks you why just say - Kids in the US marry only whom they think they are compatible with. Even in India nowadays, everyone marries only after some basic compatibility checks. What to do? We have to flow with the water, no point swimming against the tide!
Be happy and confident while facing those questions. Also, add positives to nosy questions, trying to put you down. Never say anything negative about your daughters choice.. She is very happy, what else we need? We are so happy for them. Also, add that your son in law is a great person or whatever it is. Also, try to divert them to other topics.
I have perhaps a couple hundred of my immediate and extended family settled in the US starting from the 1960s. With about 4 exceptions everyone has remained in the US. Kids and grandkids are powerful motivators to live nearby. Good finances are a must though, especially if you have significant medical needs.