Mildly Interesting

I feel I can explain this discrepancy with a bit of history.

TL;DR in the last paragraph.

The EU has a numbering system for additives, preservatives, colourings etc that have been tested and approved for human consumption, so instead of putting Sodium Sulphite, you can put E221. They used to be very very commonly listed in ingredients in the UK. The difference between Sodium Sulphite (E221) and Sodium Hydrogen Sulphite (E222) is unclear and unimportant to most consumers, so manufacturers just listed the "E numbers" instead.

In the UK, when it was discovered that certain food additives can trigger conditions such as ADHD, instead of naming the specific chemicals that were causing the problem, the British media just called them E numbers.

Cue a fair bit of hysteria about how E numbers are harmful and some legitimate concerns, and suddenly the public start checking their food to see if it has any of those nasty E numbers, and they find to their horror that a lot of processed food contains a lot of E numbers, because preservatives, flavour enhancers, food colourings, sweeteners make food more appealing, and people re-buy appealing food. Suddenly it's very much in the manufacturers' interests to name the chemicals instead of the shorter E number so even today in the UK it's more common to name the chemical than the E number, which was never required anyway. To prevent hysteria over "chemicals" in food and to inform, it's become common to label then with their purposes - flavour enhancers, colours, preservatives etc.

There's still some really quite noxious chemicals that are perfectly legal to put in food. My son's A-level chemistry teacher saw him drinking the same brand of squash every day and commented "You drink a lot of that. Are you sure there's no aspartame in it? There's no way I would deliberately put aspartame inside my body." Make of that what you will.

Anyway, the media storm around E numbers dies down because the manufacturers largely just avoid naming them that way, and carry on pretty much as before. Some kids have had reactions and occasionally news stories come out, but the media persist in avoiding using chemical names.

There's some perfectly sensible advice that says that it you eat less processed food, and especially less "hyper-processed" food, and instead eat more food made from more natural ingredients, you get a more balanced diet with better vitamin and mineral intake, thus feeling feeling fuller for longer. (If the food is designed, with proper experimental testing, to get you to buy it more, it is inevitably also designed to get you to eat it more than you need to.)

But how can you tell if the food is processed or not? What's the difference between me spending half an hour mixing the ingredients and then mixing them for me and precooking it so I just bung it in the pan? Well, a random member of the public almost certainly has salt and pepper, maybe even a few herbs and spices, but probably not any L-alanine. Look out for ingredients that you wouldn't use at home, they're probably a sign that it's highly processed.

Hence the nearly good information that there aren't any artificial flavours or colours. Nearly good, because it doesn't mention preservatives and nearly good because it is definitely and certainly processed food designed to maximise profits rather than health.

So the UK food processing industries continue to aim naturally for maximising re-buying which includes reassuring the consumers that this is the healthiest (pre-prepared, highly processed, addictively tasty) low-priced convenience food they can, whilst being attractive to supermarket profits with longer shelf lives. If the bacteria and mold-killing preservatives aren't as kind to human biology as just making it yourself and eating it sooner, and a few people have had reactions, it's just not obviously bad enough for it to be something people will do anything about.

**TL;DR ** So, my understanding is that the hysteria about artifical flavours and colours was highest in the UK and the folks from the other countries aren't looking for technicalities to reassure them about the ingredients because they were never trained by their media to hunt for nasties in the small print - those that care can see straight away this is very firmly in the processed food category, and those that don't, don't.