>plastic silverware
I've always found that strange. For non US readers - (silverware=cutlery), so our plastic cutlery (knives and forks, spoons) would be "silverware" - do you get free silverware in yoghurt pots?

Along the same lines - state room (on a boat) = cabin, I was expecting Louis XIV funiture and gold plating everywhere!

>fresh frozen
We were given some Betty Crocker cake mix which had "with artificial flavorings" proclaimed proudly across the pack

- we keep quiet about that kind of thing here - it's usually buried deep in the small print.

>friendly fire
You can just see the smiles on their faces, can't you!

not quite oxymorons but along the same lines:
here:
>farm fresh eggs
= eggs from battery hens who have never set foot in a farm
> home made (on pub or service station menu)
re-heated frozen food, made in a factory