I'd joked about Mexico annexing my house, but ...
I do not see any conditions in the Gadsen or Guadalupe Treaties about what their status is in the event the US's sovereignty is in question, however what I do see in the treaty is that in the event of a dispute between the US and Mexico, the parties are NOT to interfere with houses of worship on the territory or take actions that cause Indians to have to seek new homes, both of which have been done (to churches in California) and to me personally: My residence is within the boundaries of the Gadsen treaty, I am (part) Indian , as well as an FM3 in Mexico. If even 1/10000th of what I have said here is true than the US has violated -- quite forcefully -- the Guadape Hidalgo treaty and pretty much engaged in war crimes against an (again, part) Indian on said territory where it might be questionable whether that territory is even the US'es in which to sell to foreign hostile nation state actors, or to engage in various crimes against humanity on its inhabitants. I guess the US ha