For me, it has to be the UK since British food tends to be heavily processed along with a fixation on fish & chips, bangers & mash, pies and pastries with high fat content (most feature at least a fried item beside them, whether it’s an English breakfast with a hash brown) but not on the level of unhealthy to that from American cuisine.
Hard to say, there’s a decent amount of fried food in most places. Iceland has its fair share of sugar in the diet but I’d guess the UK in a pinch.