I suspect age distributions are part of the story. Also the Eastern US (where most of the population lives) experiences much larger swings in temperature between winter and summer so maybe people are just more prepared for it.

It's not the most convenient format because of their idea of what constitutes a region, but yeah, the US has a pyramid shaped population pyramid, while European regions have a big bulge of old people: https://www.cia.gov/the-world-factbook/references/population...