I don't think it's a US vs Others thing, it's just international longhaul vs short travel. Food on AA or DL international is more or less identical to BA or LH.

Food on european short hauls is just as bad as anything I've seen in the US. Even in business class

For economy class food, Turkish and Emirates are above the rest IMHO. But then again, maybe that's just my preference for mediterranean food

Regarding what's "bad", I'd say that it has to be very salty because your sense of smell/taste doesn't work properly in the dry low-pressure cabin environment. And then it's the general issue with any ready-to-eat meal - you can pimp it up with as many slices of foie gras or truffle shavings, it's never going to be as good as even basic fresh food