But I'm pretty sure "US" is only allowed because it matches the common word "us", rather than as an acronym for a nation.
Of course now that you've raised the point, I'll probably have to waste some time today working out a simple word name for myself.
> I found myself wishing that Munroe had allowed himself a few more terms—“Mars” instead of “red world,” or “helium” instead of “funny voice air.”