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.
I mean, you could rephrase this as “Which cuisine in Europe has the most fried foods, processed meats, sugars, alcohol and other processed foods.”
This will put Mediterranean cuisine pretty high up on the list of healthiest but it still neglects the “cuisine vs diet” question.
Malnourished people will be much better off trying eating Greek yoghurt than a bag of chips even though energy will be similar.