You are correct in noting, "Since the Civil War, US law has been in favor of an inseparable union of the states." As Hawaii is a state, it is American as long as the Union is in existence. Despite Hawaiian separatist fantasies to the contrary, international law supports the American ownership of Hawaii. There is no legal Hawaiian Kingdom currently. It is indeed in the Union.You are also correct in noting that Puerto Rico and American Samoa may be able to gain independence. As long as they are territories, independence is an option. If they every vote to join the Union as Hawaii did (and are accepted) they will be American forever. - Michael