Leone's titles evoke the traditional fairy-tale; one of universality by means of fabricated (fictionalised) nostalgia. It's a very romantic gesture (West and America are both romanticised, historical epics to both their historical period and respective genres).

I'd assume the China trilogy takes its title from Leone's, actually.

Shane Meadows directed Once Upon a Time in the Midlands a few years ago, a throwback to the Western (and Leone's in particular) set in a humble, mid-England contemporary town. It's an awful film.