On the other hand, a lot of US based businesses work overseas with connections back to the US. Those businesses would likely be affected if there are major cable cuts, and hurting US businesses hurts the US in general.

I ageee there's ways to make this work, but there would be significant disruption for quite some time as business adapts.

China would likely be fine with fiber cuts. The GFW already limits access to the world at large and encourages local hosting. One of the techniques to discourage use of certain sites is random disruption, which trains the population to look for local sites when foreign sites don't work. Russia is pushing towards a more self-sufficient internet, but I don't think they're as far along, and I haven't heard of as much opaque coerciveness as in China, although I'm sure it's planned.