Not many. Contrary to the endless click bait articles from content mills like Insider.com, about 400,000 Americans have retired abroad.
If we used age 65 and above as a proxy for “retired” people, then about 3/4 of 1% (yes, less than 1%) of retirees have retired abroad.
That is pretty close to zero!
Another way to look at this is to ask how many Americans receive their Social Security benefits outside the U.S.?
About 450,000: Some Retirees Are Saving Money By Moving Abroad | Entrepreneur
About 48 million Americans receive a Social Security retirement benefit, which works out to just under 1%. (Note – some people under age 65-67 receive Social Security benefits. And those born since about 1959 will not receive standard benefits until about age 67 and may not choose to apply for benefits until age 67.)
A huge issue for American retirees is Medicare. Medicare does not cover health problems outside the U.S. Those that move may continue to pay their Part B (and other part) premiums, but can’t use those services while abroad unless they return to the U.S. However, if they decide not to pay their Part B premiums (or Medicare supplement plans), they face a host of hurdles upon their return. Specifically, if you do not have a company/employer provided benefit while abroad, upon return to the U.S. you pay a 10% Part B premium penalty for each year past age 65 that you were not enrolled – for all future premium payments. Second, to sign up for supplement plans upon your return, your enrollment will be subject to “medical underwriting” which is an obscure way of saying that your pre-existing conditions might not be covered or might incur higher premiums. See also: Medicare and moving overseas: What happens if you disenroll? | Live Well (archive.org)
If you plan to move overseas permanently, then fine. But if you expect to return to the U.S., you may find yourself with no supplemental coverage options and much higher premiums for Part B if you do not continue your Medicare coverage, even while overseas.
Consequently, for most Americans, moving overseas at retirement – if intended as a temporary move – can become expensive.
This is likely why less than 1% of American retirees live abroad. It makes far more sense to travel abroad when you are young – and age-based insurance is several times cheaper.