I think that's unkind. "Decent" isn't a difficult bar to clear and I think many countries succeed; fundamentally, "decent cuisine" needn't be much more than "something most cultures would cheerfully eat if they were hungry." As "comfort food" the world over has similar characteristics (heavy on the fat and carbs, light on the vitamins) I think the more cosmopolitan the culture the more likely their food is going to be unhealthy.

The stuff that isn't intended for ex-pats and tourists is where things get gnarly; the stuff intended as a hazing ritual for ex-pats and tourists is where things get really gnarly. I would hypothesize that the French and Italians don't have much in the way of "really gnarly cuisine" because you aren't ever going to be accepted as a native no matter how much rotten shark you eat. I would further hypothesize that the British and Americans have more fat and carbs in their food because they spend more time in the land of lowest common denominators. The stereotype of 'Mexican food' is heavy carbs, heavy cheese, heavy meat, heavy grease but that's really "Mexican-american food." It, too, is a lowest common denominator of a number of cultures artificially melded into one for purposes of foreign consumption. The British ideation of Indian food is similar.

Meanwhile the French and Italians have a lot of really good, really stable cuisine that you can eat all the time (assuming you can put forth the effort to cook it) without clogging your arteries while the British and Americans... don't. Not really. I think the Americans don't because everyone in America either came from somewhere else or had their culture ruthlessly stamped out by invaders. I think the British don't because their culture has been import-based for 400 years and every bit of spice or flavor that got imported needed to be balanced out with a Spotted Dick or a Yorkshire Pudding or a Brown Windsor.

And I think the British spend a lot of time convincing themselves of the superiority of their dreck because absolutely no one agrees.