No, there is no legal requirement that a person be a U.S. citizen to file bankruptcy in the United States.
Pursuant to Section 109(a) of the Bankruptcy Code, “only a person that resides or has a domicile, a place of business, or property in the United States…may be a debtor under this title.”
There are court cases where a person filed bankruptcy, and they didn't even live in the U.S., they owned as little as a checking account in a U.S. bank. Also, our office has filed cases for U.S. citizens living abroad, that own property in the U.S. So if you are an "expat" or expatriate, you are still eligible to file bankruptcy in the U.S.