By this logic, a company should be free to launch a nuclear missile at Russia from US soil, as long as they pinky promise to accept legal liability for what follows, right?

When the potential damages of an action far outweigh what it is even conceivably possible that the entity doing the action could ever hope to repay, the standards for preventing that action change.

Not sure what your hypothetical proves other than that we agree that launching nukes is bad. :P

The company is still at fault and should still be legally punished within the local legal system. The difference is that the government has now got to accept liability on the international stage, since the company is incorporated in that country. The liability has "expanded", not changed from one entity to another.