The United States has not had capital controls (i.e., restrictions on the ability to move money out of the country) for a long time. Here is an article about what it’s like in Iceland where such restrictions exist.
By curious coincidence, the last few years of tax law and tax enforcement are propelling the United States to a position where currency restrictions will be easy to implement.
If you can’t send your money abroad, at least you can jump on a plane and leave the country, right? Well, funny you should mention that.