Honestly. 51st State would probably be your best bet if you actually want something approaching Sovereignty and domestic control of your own affairs. At least to the extent States can direct their own affairs.

American interest in its own National Security. Will ultimately see the U.S making both formal and informal gestures and attempts to influence any theoretical Nation State. And frankly interfere in your domestic affairs to an extreme degree. Not that we don’t already to varying degrees but I digress. Downside of living next to a Super Power.

Texas was a republic before it became a state