For the outdoor life you describe I would think Scotland. Many decades ago (70's and early 80's) I used to work for an American boss and we became good friends and kept in touch long after I had moved to America and he had retired to Pitlochry in the Highlands. He loved fishing and golf and had a wonderful life in Scotland after he retired. He lived well into his 80's so all that outdoor life and fresh air must have suited him.
Unless you move to an area close to an American base I doubt that you will find communities of Americans hanging out together. Certainly if you want to avoid large cities and live in rural areas then you are going to have to live among the locals, and you will always be an outsider, but that would apply to all non Scotts moving to Scotland, all non Cornish moving to Cornwall, all non Welsh moving to Wales, etc etc. My wife discovered a new, older, sister earlier this year who had moved from Manchester to Cornwall 52 years ago. She says she loves it there but has always been considered an outsider, including her children who were born there. She was absolutely delighted to discover that their father was born in Cornwall and came from generations of Cornish folk.
As we say in Yorkshire, "There's nowt so queer as folk", which just means that people are unpredictable, but I'm sure that you will be welcome just about anywhere.