Hah, that's one way to describe it. There are pieces of the Netherlands inside pieces of Belgium inside the Netherlands, e.g.: https://www.google.com/maps/place/51%C2%B026'55.8%22N+4%C2%B...
Why not? The bit can store male/female and you can leave it NULL for "prefer not to say".
"Between Emden and Delfzijl, the Ems forms the border between the Netherlands and Germany and is subject to mild dispute: the Dutch believe that the border runs through the geographical centre of the estuary, whereas the Germans claim it runs through the deepest channel (which is close to the Dutch coast). As the parties are now friendly states with an open border, the argument goes no further than an agreement to disagree.
It became an active issue in late July, 1914, when the Imperial German government began plans to mine the whole of the estuary that they claimed, in preparation for the launching of the Great War. The Dutch envoy in Berlin, Wilem Alexander Frederik Baron Gevers tactfully announced the boundary was uncertain, and that the dispute was "opgeschort", which could mean either 'suspended' or 'resolved', depending on the context. The Dutch government endorsed the ambiguous declaration, thus relieving itself of an obligation to declare war on Germany for violating its neutrality. After the war, the dispute was resumed."
Current status is that the two countries have formally agreed to disagree (https://www.dur.ac.uk/ibru/news/boundary_news/?itemno=22677)
For example here in Norway we have, as I understand it, bilateral agreements that allows police officers from the other Scandinavian countries to enter Norway for search end rescue, and in some other cases if it is an ongoing situation. They may also request limited police authority in Norway by calling the local head of police (a relative quick and informal process).
"The Schengen Agreement also permits police officers from one participating state to follow suspects across borders both in hot pursuit and to continue observation operations, and for enhanced mutual assistance in criminal matters."
>Seventy percent of the land of the Angle is held in trust by the Red Lake Indian Reservation (Ojibwa).
It sounds like 70% of the land is not the U.S. Government's to give.
Notice how carefully I worded my comment:
>70% of the land is not the U.S. Government's to give.
"The federal Indian trust responsibility is [...] a legally enforceable fiduciary obligation on the part of the United States to protect tribal treaty rights, lands, assets, and resources." 
The questions of armies and building bases I'm not sure have been raised, so the legal precedents might not exist. Sufficed to say, however, that the GP's hypothetical sale to Canada would be wholly infeasible in light of the treaties between the sovereign tribes and the US, as well as the legal complexities those entail.
"Limitations on inherent tribal powers of self-government are few, but do include the same limitations applicable to states, e.g., neither tribes nor states have the power to make war, engage in foreign relations, or print and issue currency."
I'm not sure if this would prohibit raising an army per se, but what good is raising an army if you don't have the power to make war? Building bases is wholly out of the question, though, since that would involve engaging in foreign relations.
But it's somewhere else.