We lived in Germany for four years, while working for the US Army.
We had the benefits of having an APO address (US postal address) use of cheap commissary groceries, the PX for relatively cheap products. We didn't pay German taxes (which were significantly higher than our US taxes.
We received a housing allowance from the Army that more or less paid for our housing and utilities. Also, our cars were registered with the US military.
It was great, we loved being able to travel without the transatlantic flights. Also, we already had our car to drive. We even had stamps to buy cheaper gasoline for our car while in Germany.
Aside from that, we had to find our own physicians and dentists, which turned out to be expensive by US standards. Our health insurance did cover some of that, but cost was higher than back home. We were in our 40s and had kids in their teens.
Having to pay for medical and dental in your 60s or 70s would likely be expensive. Most US health insurance including Medicare doesn't work overseas like our Federal Blue Cross.
Living on the economy was what we call Americans that lived in Europe on their own. 35 years ago, southern Europe was still very cheap to live, I understand the cost of living has gone up relative to northern Europe since the EU has helped southern Europe prosper and improve its standard of living. We saw that in Portugal in particular. Still, places like Portugal are still cheaper than Germany.
Living there full time would require leasing an apartment or buying a home. Expect that to cost, especially in large European cities.
Remote areas would be cheaper, but would those place be appealing? They might depending on your lifestyle. Still, much research is required.
Buying an automobile would be expensive and getting a driver's license in Europe might be a royal pain in the butt. We found out what it took for Germans to get driver's licenses. It was way more bureaucratic and complicated than in the USA. Not sure if your US license would work for long if your residence was in Europe.
Groceries are more expensive in Europe than the USA. VAT taxes can be significant, depending on where you live.
Language could be a problem in dealing with basic living, like getting letters from your local government or tax office.
Other things that we found in Germany that could occasionally be irritating were that if it snowed or iced up the sidewalk near your house or apartment with outside sidewalk, you were responsible for clearing ASAP. Also, German law required you to notify the police when you moved to let them know where you lived. There is more stuff like that to deal with in foreign countries.
Living overseas is fun, and we enjoyed our time there with all the travel opportunities, but life if different there. Parking in cities can be hard to find and expensive. People are expected to take public transportation, which may be another issue to adjust for.
We still enjoy traveling to Europe, Asia, South America, Australia, and other places in the World, but still love coming home so we can see our children frequently and enjoy things like college football and visit great places in our own country.