Mmm. I don't know about Heroes being uniquely American, but I think its style—big, grandiose, Earth-shattering, global-consequence–having—is a primarily American style of storytelling. You rarely find stories of such ambitious scale in British TV series, for example; perhaps that's because we're (1:) a tiny country and (2:) aware that other countries exist. (I kid.)
We have had some similarly ambitious series over here, things like Doctor Who and Torchwood, but their style's been heavily and consciously influenced by American series like Buffy the Vampire Slayer. Kind of like the American version of The Office: it's an American programme but consciously draws on a British type of humour (specifically the original series).
British speakers seem to use “Western” in much the same way, though less frequently. Anything about modern, city-dwelling life, and particularly modern technology, can be characterised as “Western”. I guess it's a way of making sweeping generalisations whilst excluding poor people living in South America, Africa and Asia.
(Editor's note & hyperlink-juice on the Post of the Week thing: I nominated a post on Sarah's blog for Post of the Week (which I discovered when I was nominated myself) and it co-won.)
Thanks for taking the time to write, Bob.