Islam prescribes that you obey the laws of the land as long as they aren't forcing you to divert from Islam. If you want to marry a girl of the people of the book, you should marry her according to Islam and then register the marriage according to the laws of the United States.
If you then want to divorce her, pronounce "talaq" once (loudly in front of her) and that would be counted as a divorce according to Islam, then officially divorce her according to the laws of the United States.