Gay couples have already had divorces in the USA. The federal government requires all states to recognize marriages performed in other states. (A leftover from the early 19th century when many states prohibited "white" people from marrying negroes, Chinese or Native Americans. The U.S. Supreme Court eventually nullified these prohibitions... but not until the 1970s!) So if you and your same-sex partner were married in Maryland but then relocate to Alabama to find work, and then decide to end the marriage, the courts in Alabama have to let you file for divorce in that state.