Honestly, this sort of action just seems like a return to the status quo; you can say what you want, and people who read a lot of embassy press releases might see it, but good luck finding a newspaper who’ll cooperate if it’s abhorrent stuff like this.
Twitter could just let the tweet exist for people who personally choose to follow the Chinese US embassy at no cost to other tweets. I mean, it's from a national government's embassy, their angle is not hidden at all.
Now they open themselves up to all sorts of questions, are they softer on the Saudis? On Israel?
Getting into picking and choosing which foreign governments are allowed to post, and which messages they'll countenance, at additional expenses for their mod team? Twitter has a foreign policy?
[0] I don't actually have a newsletter.
Twitter has to obey the law, other than that they don't owe that embassy anything.
You'd obviously see similar arguments about keeping Trump's account. What if the leader of a country calls for violence? Keep it because diplomacy?
As someone else mentioned and I now agree with, Twitter isn't an arm of the government. It's a U.S. company that has rules. Government officials can use any platform they want to get their message out. Companies can mostly do whatever they want with their own platforms.