Does The Low U.S. Death Rate Mean Our Efforts Are Working?

Peter Wallison argues in the affirmative.
However, I've been wondering whether we ought to control for population density, too. Maybe even proximity to other hard-hit regions.
I'm not sure he's right to say that we should compare countries on the same day. It would seem to be better to compare them from something roughly like the day the first case appeared there, or the day that 0.01% of the population was infected.