I vote hanger. I'd be more likely to believe it was a worn chain/cassette if it did it in the heavily-used middle gears, or if the chain was actually slipping under load. Here, we have a chain that's jumping a bit as it catches a tooth funny when pedaling under no load. Big difference.

The fact that it's doing it on the smallest cogs is telling too, because that's where the chain's most sensitive to alignment. My guess is that the chain isn't jumping because of a stuck link, because it's doing it way too often, much more than once per chain revolution. Rather, it's catching one of the profiled teeth on the 11 or 12t cog due to the hanger being misaligned. Add in the fact that there was a recent crash, and there's where my money is.

Note: I particularly recognize this behavior because my own bike used to exhibit the exact same thing, and it definitely has a bent hanger I haven't bothered to get fixed yet. I was able to tune most of it out, but every bent hanger displays different characteristics so no guarantee for you. You might be able to get rid of some of it by tweaking the b-screw to push the RD body away from the cassette, which will ease up the angle of the hanger misalignment.