Could have something to do with how you define a nation-state.
How do you define a nation-state?
I used the words "charting its own course." I would include that as part of the definition, along with other things, but seeing how the general OP is pretty aligned with the concept of economics, no need to get into the others; however, in addition, if you like, we can also add the US is truly no longer homogenous in any sense of the word.
Since the US government does not solely direct (in fact, it has no current role) its monetary policy, it does not meet the definition of a nation-state.
So, overall, the current state of inflation is not really inflicted upon any citizens of any country by the people occupying governmental positions of authority, including Joe Biden. It is facilitated by these people at the behest of those responsible for establishing the monetary policies (i.e., central banks).
A country owning its central bank would continue to meet my understanding of the definition of a nation-state.