People didn't stay quiet about HW because of some general difficulty of denouncing atrocities, they did so because he wielded significant influence and they didn't want their careers to suffer. This is sadly true of the victims as well: more than one of them has said that they wanted to go loud and public with it but were afraid that it would completely wreck their career through being blackballed, etc (and some of them have said that this _is_ what happened as a result of coming out with allegations).

That doesn't apply at all to the US failing to denounce e.g. Indonesia.

This misses the point, because the people standing up for Weinstein would be more like people in his own state in Chomsky's example. They were close enough to do something about it.