>Is this an American thing or something? Almost all the cats I've ever known were outdoor cats in the UK.

I can't speak for anyone else, but I'd never allow my cats outside.

Not for ecological reasons, but because I live in a flat on the fourth (that'd be the third floor in the UK) floor of an apartment building in NYC.

If my cats got out of my apartment, they'd have to go down three flights of stairs and then wait for someone to open two separate doors in order to get out into the street.

Once on the street, there are many hazards for cats, not least of which are automobiles.

Having been to London, I imagine that there's a similar dynamic there as well.

As such, I'd say that it's more about urban/suburban/rural settings than different countries.