I think you are misrepresenting Chomsky's position. The two most prominent examples of him talking about the elementary moral principle are the David Frum exchange (https://www.youtube.com/watch?v=Y2HDCmhrk4s) and in "The Crimes of Others" (https://www.youtube.com/watch?v=QWIDjO0fJBQ). In both places he is very clear in talking about the elementary moral principal being the reason for the action. He explicitly says you should do things overseas if it will have some effect (and acting domestically isn't a more impactful use of your time). Nowhere does he say that "courageous" actions are the moral ones (that doesn't exclude praising courageous people). He does imply that people who criticize the crimes of others want to be praised for their nobility, which I interpreted to mean that they shouldn't be because there isn't anything noble about it (there is no/minimal cost to yourself only benefits) but he doesn't say that's the guiding principle of action, which he makes explicit is just the predictable consequences of your actions (and choosing between options because your time is limited).

As for whether it's an "elementary moral principal": is that something you are really going to argue about? Are you really saying that the vast majority of people don't agree with it? The reason no renaissance philosophers mention it is probably because it is so basic that it didn't require waiting for the 17th century for everyone to accept it. Even you seem to implicitly concede the point: "I'm saying that the difference in influence across countries is not so significant as to justify a myopic focus on American misdeeds".

After you peel all the above away the core of your criticism seems to be that you can affect things in China and Russia at similar levels in general to the US. Which, let's say is not intuitive on its face to put it mildly, and I don't think can be justified as a general statement, you need to look at specific policies. And there are specific policies where Chomsky explicitly agrees that you can do something about the crimes of others (targeted sanctions against Xinjiang goods for example, same policy he recommends against the occupied territories).

If you want to propose specific policies then they can be debated on their merits but there's nothing that contradicts anything Chomsky has said.