The impression I have from talking to Americans is that to eat good food in the US you need to really make an effort,

I promise, not anymore than the US. Actually, I'd argue especially in less urban areas getting fresh ingredients is more convenient from the prevalence of driving. The problem is if you can't drive you're screwed.

Yeah, I too think it's a mix.

You see some kinds of shit food also being pushed in Europe, and then you see different outcomes per country, depending on local food culture and also legislation - people expect some thing and won't settle for less plus certain things are simply not allowed by Law to be sold as food or be branded in some ways (for example, there UK has very strict demands of what can go into what can be called a "sausage", which is why the shit stuff is called "bangers").

Also in Europe vs the US you see a major difference in where farming subsidies go to - if more traditional farming is subsidized instead of corn raising and hormone-filled cattle breeding, the better quality stuff is what's cheaper not the crap stuff.

For starters, you seem to be falling into the trap of comparing the food you eat when you visit a place and go to restaurants with the food you eat at home and have to cook from available ingredients.

No. I lived in the US for the first 18 years of my life.

unless you’re talking about the local culinary tradition alone

Sort of both, of course metropolises will have a lot of immigrant cuisine, but I've found at least in continental Europe(I can't speak for the UK) that immigrants often tone down stronger flavors in restaurant food- immigrant foods I grew up with are also harder to find in Europe(Czech Republic doesn't have any Ethiopian restaurants for example, and at least the ones I went to in Vienna were not very good).

the US to doesn’t really have a local culinary tradition

That's simply untrue. Just because foods had foreign inspiration has nothing to do if its locally american food, from Chinese-American Chinese food, to American Pizza, to more traditionally american foods like chilli and gumbo(and other cajun food), american style bbq and fried chicken- etc. Tempura being based on fried foods brought by Portugese doesn't make it not Japanese.

As for the rest, in my experience all large international cities in the West

What does the west mean to you? But yeah I would agree large international cities all have immigrants, though I would argue the US has much better coverage of a variety of foods in smaller/medium sized cities. But that's also not exactly relevant. I didn't say the US as a whole is not terrible compared to large international western cities, I said compared to the rest of the world- then mentioned specifically countries(or regions) that I believe to have blander food than the US(on average).

(Even smaller places like Berlin, Amsterdam or Brussels have great variety of food in restaurants).

... Smaller places are not capital cities of major countries for the most part. And those are actually bigger than many European capital cities, and Berlin is very large.

The point I’m making is about the “average” (hence why I actually used the word “average” in my post),

You're talking about the average but listing above average cities. Compare Louisville, KY, a very average american city in terms of food, size, and income, to Prague, CZ, a capital city twice the size- there is far more variety of food available in Louisville, the only thing keeping Prague alive in terms of options is the Vietnamese immigrant community.

not the way outside the average places which are the main cities and it’s about the food people normally eat, and that doesn’t mean the restaurant trade

Again, I have found more variety and quality of produce in stores in the US- stores that I tend to go to in the US also tend to have more variety in general. But that's mostly because in the US its common to drive to larger stores, rather than going to smaller local stores- and big stores in Europe also of course have a lot of options. (Something very weird though, I was cooking chilli for my partner and I- and we could only find ground beef mixed with pork in our local grocers and not purely ground beef- but that's just a weird quirk of our area.)

which tends to be great pretty much in any large city of the World in any nation rich enough to attract people from all over the place.

From restaurants that tend to be affordable? No, I don't agree. I keep mentioning Ethiopian food just because its something important to me that would be impractical for me to cook myself, but all of Poland didn't have an Ethiopian restaurant until about a year ago. (Granted the one that opened in Warsaw now is very good.)

The second reason is that while both the US and EU have farming subsidies, the way these subsidies are structured means that in the US they tend to incentivize the use of high fructose corn syrup

Yes, but that is actually not solely subsidies- but also overregulation. Sugar imports are taxed. Though, it would be better for people's health to try to transition away from caloric sugars to substitutes like aspartame.

the production of highly processed foods

Source?

highly processed foods tend to be more expensive and “whole foods” tend to be cheaper.

This is just the blog of a guy selling a book.

As a result people in the EU tend to eat less processed food as a percentage of their caloric intake:

So we were talking about supply, not consumption. But regardless, yes americans choose to eat processed foods more on average. So? The predominant cheap form of calories/proteins in Europe are cereals and tubers, those aren't exactly lacking in the US. (Btw, its just because they're cheap everywhere,

Though its not like either Americans or Europeans are significantly different in food group consumption for the most part The other differences being a much higher preference for meat in the US, also supported by the US actually getting majority of its protein from meat sources

Americans can afford raw potatoes too, they choose not to buy it. In fact, despite buying meat something supposedly 25% of Europeans cannot afford to eat every second day(though I don't believe that statistic to be honest)- Americans spend significantly less of their budget on food.

And to preempt a possible argument, American antiobiotic use in livestock is on par with some of Europe and much lower than some of Europe

Yep, but this discussion is specifically about quality

You're confusing cheap chain restaurants with American culinary?

As somebody else pointed out in the other place you quoted that metric, that metric is about the likelihood of food contamination, not about the food's nutritional value and certainly not about how healthy it is in the long term.