Why those 3 countries in particular? Wouldn’t this work anywhere (provided it’s not in a war zone or a volcano zone etc)?
You could always settle in the Mojave, plant a grove of bristlecone pines instead.
I don't know if more boreal climates support longevity, I think it has to be some combination of temperate + dry + safe from natural disasters like wildfires and hurricanes
Even for other kinds of long-lived trees, places without big ice storms, hurricanes, etc. that would prematurely end the tree are probably safer bets.