My parents are immigrants and I grew up in the US. My husband and I have some dual citizenship options that would allow us to potentially move to another "developed" country without huge hassle, and we are definitely considering it. In our case, the COL difference probably would not be huge, but we see a lot of value in having more of a social safety net (particularly with regards to healthcare). I get the sense also that (though this could just be my perception) that there is more respect for basic living "rules" in some other places than there is in the US, which I think may actually contribute to making those places more functional. Like, in our neighborhood/city, people think nothing of parking on the sidewalk (making things difficult for pedestrians and DEFINITELY creating problems for anyone in a wheelchair or scooter), jaywalking, leaving trash out at the park, etc. None of these things are necessarily huge on their own, but we find there's a kind of pervasive attitude of entitlement like "I should be able to pick and choose which rules I want to follow". I don't necessarily want our kid to be a mindless compliant robot, but FFS, some of these rules/norms DO actually result in a greater benefit to society overall.
As far as education goes, there are good university options in any of the countries we are considering and I personally feel the US university system is on a fairly unsustainable trajectory right now, so I don't feel that staying in the US is necessarily going to benefit my kids educationally. I also think that if the US continues to choke off immigration that it might start to lose some of its edge as the world technology leader.
We do plan to FI with enough of a stash that if we went abroad and it turned out to be a terrible idea, moving back to the US would still be feasible.