Puerto Rico has sufficiently different circumstances to not make this an apples to apples comparison. They already owned the land when they were independent of the United States. There was no state of Louisiana independent of the United States and the overwhelming majority of people who live there are descendants of US settlers.
What about the land belonging to the original thirteen states? If, just for the sake of argument, one or more of them wanted to leave and if it could somehow be done fairly easily and amicably, would those states have any claim to land or resources they possess under the current system? And if the Union holds that newly admitted states have the same standing and rights as older states, could they make the argument that such an arrangement would be due to them if they wanted to leave?
Well, just a little bit of history and then I'll give my answer.
The Commonwealth of Virginia started as a colony founded by the Virginia Company based on a charter from the Queen or King (I think the charter was under Elizabeth, but the first permanent settlement was under James I). The charter gave them what we know as Virginia, plus Kentucky, West Virginia, and what was called the Northwest Territory (essentially the Ohio River Valley, Illinois, Indiana, Ohio, parts of Michigan). I'd have to check, but it might have been given land all the way to the Pacific coast.
When the Revolution took place and they declared themselves independent states, there were obviously some conflicts over who got this territory. Virginia, Pennsylvania, Connecticut, and probably a few others all felt they were entitled to the Northwest Territory. To resolve this dispute, all the states agreed to cede this land to the federal government. Over the years, other land has been ceded to the federal government for military bases, government facilities, etc. If Virginia were to secede, they would not be entitled to this land any more than they would be entitled to Ohio. Now this is different from whether they would be allowed to secede at all. As I mentioned earlier, Virginia entered the Articles of Confederation, which said the union would be permanent. However, if the situation were grave enough to be comparable to that of the American Revolution, I'm not one to rule out absolutes.
... Puerto Rico is not integrated so there's no disruption from severing it.
Most likely there would be disruption if a state left.
That's a bit naive, isn't it? After all, we're talking about an integrated economy. You mentioned one area taken as a given that clearly won't be. Just using Louisiana as an example, a sovereign nation generally is recognized to have a certain maritime border. States are not recognized to have this border. This leaves a stretch of water currently owned by the United States not in Louisiana. If Louisiana were to become a sovereign nation, they might want this territory. Currently, the United States has this territory and they have a certain expected revenue that comes from leasing this territory and another set of revenue that comes from the taxes of the US companies that drill there. Furthermore, those US companies are used to certain Federal laws applying and, where Louisiana law conflicts, Louisiana law is preempted. There's a benefit to that certainty that would go away were the federal government to lose jurisdiction over the area.
I understand there was animosity when the Republic of Ireland was created, the British got over it.
You realize a time period known as "the Troubles" that has led to violence that continues to this very day is probably not the best example of "amicable circumstances," right?
