My theory - they got popular in the US because everyone was still microwaving stuff like it was 1980 because their electricity is girly 110v so they can’t have good ovens. The air fryer is an improvement on both those things
In modern countries with 240v, everyone bought an air fryer cos the yanks said they were amazing, and now they’re scared to admit they fell for marketing hype and it’s just the same as their fan oven that they’ve had for 20 years except it heats a bit faster and they can’t fit stuff in it
From what I’ve seen in the comments it’s “Americans discovered an alternative to a microwave”.
Hate to break it to you, but most oven ranges in the US are 240V. They have 240V into the home which gets split into -120V and +120V lines with a neutral in the middle for regular appliances. Bigger appliances can get wired up for the full fat 240V experience
I’m guessing its more to do with the size, ovens in the US are massive! Probably double the volume of a regular EU oven