Yeah, though I’ve read that it’s also true for the UK. I speculated in another comment that it could be from how urbanization and industrialization went in Europe, where people were displaced from traditional sources of spices and thrown into an environment where there weren’t really alternatives/replacements available, and the traditions have just further atrophied and been annihilated over the generations since with fast food and ready-made foods in stores catering to those atrophied tastes and just stacking more salt, sugar, and fat into things instead of going for flavor. In other places urbanization and industrialization were more abrupt and happened in a context where spice production was already industrialized, so tastes remained largely the same and their respective fast food and prepackaged food at least tried to mimic that to some extent.

I also can’t help but assume that ludicrously cheap meat was also a big factor in food becoming blander in the US, at least, because it was an excuse to be lazy and not learn to cook when someone could just throw a cheap piece of beef in a pan with maybe some salt at the most, then douse it in red corn syrup that maybe had a detectable bit of vinegar in it, and it would be palatable enough to eat even if it was bland and mediocre.