This isn’t the us army making the argument or the American state. Normal people are.
How is this different from saying “only people who have never sinned can speak out against evil.” With the added dollop of whataboutism?
You can't make a moral argument ("China is evil!") without being on moral highground. Having your own moral highground questioned when you're trying to paint youself as better is not "whataboutism".
There's two way how you can go about this argument:
1.) You can debate purely realpolitik - where morals don't matter and only the benefit of US or China hegemony is taken into account. This can be a hard sell though, mostly due to how current administration relentlessly attacks even their historic allies.
2.) You can debate on basis of keeping a free and modern society and how US keeps Chinese totalitarianism at bay. But then you will have to accept having your own morals questioned. Screaming about Chinese totalitarianism when the current US president actively avoids and attacks the US justice system trying to keep him accountable is hypocritical.
How is this in any way comparable to China where people have to come up with homophones/alternate words to literally get around armies of state censors?
However - if you want to make a moral argument against another side in a conflict, you need to make sure that you're actually standing on a moral high ground. At least if you want to recruit allies on your side. And, if you read the news, current US administration hasn't been treating their allies too well these last years. And US will need allies to resist Chinese influence.
I don't hold any sympathy for the Chinese, but it's also hard to see how following just another bully in an unequal relationship would benefit my non-US government.