But the reason emissions happen is for per-inhabitant benefits. It's a very reasonable idea [0] to set a per-inhabitant goal and criticize countries exceeding that threshold (which the US would still fail at, but I'm arguing against the metric itself rather than US faults).

Take your position to something of an extreme -- the Vatican could open up 200 coal power plants for its holy Bitcoin operations and still be sufficiently less impactful to CO2 than the US that nobody would target them during climate talks. Rephrased from the other direction, each US citizen would blow their CO2 budget by buying a shirt per decade to get down to the Vatican's levels.

That's a common mental failure mode, analogous to the sorites paradox. Countries are made up of many small actors and decisions, and pretending otherwise is unlikely to help you achieve your goals.

[0] Mostly -- transitive effects like one country generating all the goods another country uses are harder to account for. Assuming we could measure perfectly though...