It's relatively easy for a company to relocate employees, as long as it has a reasonable need for specifically those people. If it wants skilled employees with a native-level knowledge of the language and culture, it wouldn't be hard to relocate them. Having said that, it's entirely possible that those employees don't want to be relocated. If my company's relations soured in my country, I'd rather quit and find a new job then leave for the company.
Re relocating to the US, specifically: I've been through the H-1B visa process - I have the visa, but I never actually jumped. Quite apart from times when it's oversubscribed and becomes a lottery, there are any number of small hurdles you could fail on.
But if it's relocation to anywhere not-China, then yes, that ought not to be too difficult.
And, Google just needs to get the people out of Mainland China. If their safety is in danger for actions that they had no control over, I'm sure some country will give them asylum.
Or maybe China realizes that it lost, and will model the rest of the country after Hong Kong. (Remember, Hong Kong is technically mainland China.)
I've been through the same process, and all those hurdles are extremely easy to avoid and/or overcome if a company has a decent set of lawyers who deal with this thing. That kind of resource is easily within Google's reach, especially judging by the number of other companies who have legal departments dedicated to the process.
