Picking up on Greynomad's last comment, spackle was well-known to me when I was growing up here in Australia. I used it to fill cracks when I first started interior painting, but the problem with it was that, being made primarily of gypsum plaster, it set hard, and over time it would shrink and crack. There was no flexibility in it (unlike polyfilla), so if the house moved at all - and what house doesn't - you were back to square one. When I painted the interior of my house in the late seventies, I used polyfilla, which, being cellulose-based, didn't shrink and would cope with some movement in the house, and I've only used polyfilla since.
I understand that spackle is still on the market, but I haven't heard of anyone using it anytime recently, so maybe whether or not we know the word "spackle" is a product of time as much as of geography. If we do know it, we may be showing our age!
David