Well, any time you talk about what "China" owns, you have to ask yourself whether that is what "China" owns or whether that's what "Chinese people" own...
Two completely different things. Some rich dude in Shanghai who bought up a few million dollars worth of rental properties in Irvine CA doesn't "owe" anyone squat. Some rich dude in Shenzhen who has $25M in wealth in Wall Street stocks doesn't "owe" anyone squat. Those dudes weren't doing virology research in Wuhan or weren't strongarming the WHO to keep things quiet.
I think the $1.1T that "China" owns of US debt is likely their sovereign wealth fund, so that would legitimately be owned by the Chinese gov't.
However... Reneging on US treasury bonds, EVEN for China, may not be a great idea for anyone who wants the USD to remain the world's primary reserve currency... So it could end up hurting us FAR worse than the $1.1T "windfall" we'd get from stiffing China on those bonds.