Will my green card be affected if I marry someone outside the U.S.?

No, your green card will not be automatically affected just because you marry someone who lives outside the U.S.

 If your marriage is real and you plan to live together in the U.S., you can sponsor your spouse for a green card through Form I-130.

You must maintain your U.S. address and file your taxes correctly to show you're still residing in the U.S. as a permanent resident.