A lot of that also comes down to how far the tech for windows has improved over the years. I feel like more American homes are much newer and therefore more inclined to have newer windows than many British homes.

I personally don’t much care for stick built homes and would prefer ICFs for most situations but mostly for water and fire resistance. Stick framed houses have so much thermal bridging so I can totally see why a layer of insulation between two brick walls would be quite good.