Japan is a sovereign country. They are closely allied to the US now but that doesn’t mean it will always be the case nor that they have to silently agree to every stupid mandate the US tries to impose.
So is China. That didn't stop the US from retaliating economically when they do things the US didn't like. Just because countries are sovereign doesn't mean the US can't force them into compliance, allies or no allies.
Why do you think the US spends more on military than all the other powers combined? So they call all be sovereign from the US? Or for the US to have enforcement over world geopolitics and influence over the other powers to keep being the world reserve currency?