> The US is corrupt but not that corrupt.

By that metric, every nation is corrupt and the term becomes meaningless.

It would be like hyperbolically calling every person guilty of physically injuring someone else a “murderer”.

Every nation does have corruption. Corruption is not a binary.

Which is precisely the point. When you say a nation is "corrupt", you're generally referring to one that is notable for that factor. Because otherwise the term is meaningless (because every nation does have corruption).

As a complementary example, you could argue all legislation is authoritarian; but describing a nation as "authoritarian" in the general (vs specific, as in certain laws/bills) goes above and beyond "normal" legislation.

If every nation had it, it would not be a binary. It would be a gradient characteristic, like temperature.

And given that nations are made of people and people are corruptible, that actually sounds about right.