Rat, you missed the part about the cowboy. That was the bit that'd make me feel like I stepped onto a movie set, not being called Ma'am, as unfamiliar as that is. We have a distinct shortage of cowboys around these parts. Now surfers, we have plenty of those. If a surfer suddenly appeared and called me Ma'am I wouldn't blink; I'd just think he thought I was old.
Although my environment is not at all devoid of common courtesies, we simply don't use call each other Ma'am that often, so it sounds out of place. And instead of calling me Miss, someone who needs to get by is more likely to simply say "excuse me." The courtesy is still there, it just sounds a little different.