Some US territories have a parallel tax system that isn't underneath the Federal Government, whereas states are under the federal government, so a resident of a state has to pay state taxes as well as federal taxes. Although there are "categories" of types of territories, these categories are pretty much made up on the spot and each territory is its own separate case, as the US only has 5 inhabited territories all with unique tax and citizenship conditions.

Long story short, Puerto Rico has a tax system that is treated like being a foreign country, but checks the box for total Federal US tax compliance.

Under Puerto Rico's "Act 60", which mainland transplants to Puerto Rico can apply for, many transactions are taxed at zero percent, most importantly capital gains (for trades initiated while on the island and sold on the island, pro-rata based on time for longer held positions), while "PR sourced income" is taxed at 5%, or an up-to-4% corporate tax rate (so the same activity done through a corporation is taxed lower, and the dividends are tax free, and the sales of shares are tax free)

So if you want to clear all your money in the eyes of the Federal government, then living a year in PR to execute or finish a specific plan is good.

Congress has a little control over PR, but its more beneficial and easier to perpetuate division in Congress, at least at this class level, than pretend to have some other trendy cause that your friends want you to espouse.

and finally I made a reference to renouncing citizenship. If you leave "for tax purposes" then there exit taxes. So the goal is to keep more of your money at your own discretion, and then leave for any reason that isn't "tax purposes".