Fair enough, I’ve lived in Spain as well, no children though.

I am not ignorant of the cost you surface wrt taxes, but taking into account my total US tax burden when you add in insurance and medical expenses for a family of four, cross jurisdiction tax credits for taxes I would pay in Spain, as well as the improved quality of life around work life balance, life pace, safety of living a car free life (walking or riding bicycles primary for transportation), and so on, it is a net positive for our situation. I admit others must perform their own assessment to understand if a potentially favorable outcome awaits them.

If you want to grind and become wealthy, it’s not the place to be; it’s a place to live. As always, be mindful what you’re optimizing for.