I think something as contagious as COVID was going to get out, sooner or later, area under the curve.
I remember how hard Italy got hit early on. I think a lot of US infections came from Europe, after getting there from Asia.
It would have been a difficult thing to shut down. It might have been contained very early, but physicians have to recognize early that it is a new virus, and that's hard to do when you have a new virus. Recall the young Chinese doctor who was punished for reporting a new virus, and then died of the virus.
Initially, the Chinese hid the outbreak, which was immoral, but then when they saw what they were dealing with shut down Wuhan and isolated it, but it was too late for the rest of the world. It does appear their tactics largely succeeded in controlling spread. But, I also recall a CNN reporter was able to leave Wuhan just before Wuhan was shut down and isolated. He left because he knew the isolation was about to be imposed.
It is hard to say how successful China was in shutting it down because it is a totalitarian regime with control of the media. However, it appears the Chinese did better than most at stopping the spread. If the spread there were worse than here, it would be hard to hide, because it has been really bad here, and there are so many more people in China.
Western Olympic athletes isolated in COVID hotels in Beijing complain about the conditions in which they are isolated, a hotel room with bad food, and adverse effects upon their mental health. Beijing will have a spike in COVID cases after the Olympics, and the news will leak out. It takes a few weeks to spread exponentially.