Well let's not be too hasty. There are structures and scenic items from England that are marked OO/HO -- they may actually be halfway between the two and are probably useable. (Just as structures built to 1/8" scale are often usable in HO so long as an HO scale figure is not seen hitting his head on the top of a 1/8 inch scale door!)
The HO track we get from PECO is used for OO trains in England so again there are ways to mix some items. In England HO and OO use the same track except for some fine scale OO guys.
Some guys use British OO mechanisms for American HO steam.
If you ever see old American OO -- which used a different gauge in addition to a different scale -- you would see a noticeable difference. I once picked up an OO caboose not realizing it was OO until I got it home. It was too big to be usable. Too bad as it was a nice model.
Dave Nelson
