I think everyone has covered most of the possibilities, it seems like we probably won’t really know the answer for years, if ever. The baseline higher homicide rate is heavily influenced by easy access to firearms in the United States, but YOY changes should be comparable across OECD countries if covid quarantining caused broad cultural changes similarly across those countries. I haven’t seen enough complete data anywhere (including here) to fully understand how the numbers look in comparison.
I also think it’s worth noting a lot of cities massively scaled back enforcement targeted at lower level crimes at least in the earlier parts of covid, as it wasn’t seen worthwhile to risk cops having to do the close contact field work over minor shit. Many states and cities have released tons of people on pre-trial confinement and even commuted prisoners out of state prisons. I suspect the recidivism rate among the people in state prisons is relatively low because I think it was weighted more towards people near the end of their sentences and the older inmate population, who often have “aged out” of crime to some degree. But I think the society wide “interference” with lower levels of policing, both in terms of less arrests, people being released from pre-trial confinement, charges being dropped etc may have resulted in a lot of people who otherwise would have been locked up not being locked up. I can imagine a scenario where two guys get into it on the street and get arrested, where before they might eat a charge and be in jail for a little bit, instead the police ROR them and they meet up the next day and one kills the other, situations like that would be more common in the covid world.