Didn't see this on your list:
One major consideration when moving abroad at older age is the quality and cost of medical care. When evaluating places to live, look at the availability and proximity of quality care, look at the costs of that care, and consider if you can somehow quality for a national healthcare system.
First one is a Pro, not a con. Opportunity to broaden your perspective, learn another culture.
Second one is related to the first. It is a barrier only if you want to be. If you don't want it to be, then put in the work to learn the language and culture.
Third one is broadly related to the first two, and is not <usually> for the reason of being American. Foreigners in general get treated like shit in many areas until the locals see that they genuinely are interested in being part of the community, and not just there to be rude neighbors who exploit the locals. The ones that get hated are the ones who land in a country and immediately look down at all the uncivilized squalor and horrid behaviour around them, not realizing that they really should look in the mirror.