It's interesting that many people are describing their own ideal retirement location, without addressing the issue posed by the OP, which is the possible need to look outside the US.
Guess you're right, but we've found our ideal right here in the US, and the"retirement" word hit me as being able to have what we want, when we want it, and the "now" for us is the slow down period when the sun and the surf and the shopping and theatre don't mean as much as being comfortable and doing things at our own pace.
So, yes... we've sampled life in the Adirondak Mountains of NY,, on an Island.. (Martha's Vineyard) on the coasts in Cape Cod and Rhode Island and Maine, in Westlaco Texas, Atlanta Georgia, Chicago/Lisle IL, Leesburg Florida, Boston MA,and now in Peru, Central Illinois... with time spent in Colorado, California, Albany NY, Baltimore, MD, and a quick sampling of Tokyo... All of these places have their charm, most have been on a coastline or near water and boats and most would have been fine places for the earlier retirement years.
Now, not so much. Slower, safer, more stable, and everything we want and need within 3 miles. Our HOA is truly run by the homeowners, for the home owners, and this has led to having and keeping a beautiful well kept, treed and flowered neighborhood. Ten years ago, our eyes might have wandered to a more exciting and challenging homestead, but now, this is our home and we wouldn't want to move from it.