I think the trope is that British cuisine, that is, dishes that are uniquely British, are bad. Not that there isn’t good food there. Being a rich country, an empire, and part of Europe means you can have many, many different cuisines there though, and like you said many are very good.
Requiring something to be "uniquely British" to count as British cuisine seems like a pretty high bar. Are burgers and apple pie "uniquely American"? Not sure – and who even cares?
You’re right, and that’s not the bad I meant to set. More like cuisine that is associated with Britain. So not a French restaurant that happens to be in London.
My Romanian grandma, born in the 1920s, that never traveled more than 100km from her birthplace and never saw even the Black Sea, would beg to differ :-p
I highly doubt that my almost illiterate grandma, that grew up in interwar Romania and lived afterwards behind the Iron Curtain, discovered apple pie through American media :-))
It's a trope for sure, but it doesn't really make sense: a lot of American dishes are traditional British foods. Roast dinners with stuffing and gravy, apple pie, pancakes, biscuits/scones, fried fish and potatoes, meat pies. Thanksgiving dinner is an ancient British harvest feast with some New World ingredients; Christmas dinner is the same format.
And since most American food has also made its way to the UK, there's really not a great deal of difference.
