Earlier quoted context omitted.
The regulation would apply to the UK. UK brands and goods sold in the UK, by established/registered companies the UK. Not possible to sell any retail goods of the sorts w/o a registration in the UK, so stopping them advertising won't be hard. I don't think US administration would be able to do anything, much like GDPR.
What about Mr Beast video sponsored by McDonalds (for the sake of specificity, a new McMuffin available in every country on earth)? > I don't think US administration would be able to do anything, much like GDPR. We live in a different world to the mid-late 2010s. For better or worse, I'm fairly confident Musk and Zuckerberg will have input on US trade policy on these issues.
In a similar vein gambling content targeted at kids would have a similar approach. Keep in mind the businesses still need to be able to sell in the UK.