There are no exact figures on how many Americans live abroad. In 1999, a State Department estimate suggested that the number may be between 3 million and 6 million. In 2016, the agency estimated 9 million U.S. citizens were living abroad. However, these numbers are highly open to dispute as they often are unverified and can change rapidly.
If a green card holder stays out of the U.S. for 1 year or more or if the green card holder is living abroad permanently, then the may be found inadmissible and denied reentry into the U.S. If an American resident needs to be out of the country for a long period of time it is recommended to apply for a re-entry permit before leaving the U.S. Can You Receive Social Security Living Outside the U.S.? Feb 05, 2020 More Americans are retiring outside the U.S. - CBS News
Medicare coverage for those who live permanently outside
How to Vote as an American Living Abroad - The New York Times Sep 04, 2018
mother lives outside the United States, Form I-130; A copy of your birth certificate showing your name and your mother’s name A copy of your Certificate of Naturalization or U.S. passport if you were not born in the United States father lives outside the United States, Form I-130
The Best Places To Retire Outside the US - CNBC Feb 03, 2011 Overseas American Citizens: When You Need to File a Tax Every year, scores of American citizens who think they are exempt from the obligation to pay up to the IRS because they are living outside the U.S. are met with a cruel reality: U.S. tax law continues to apply to them, and unwelcome consequences may await those who fail to comply. So You Wanna Live Abroad? Here’s How Taxes Work