There's another surprising reason why per capita numbers aren't useful - for exponential growth on the typical type of graph starting at some "initial" number of cases, it makes no difference! For example, if one country was counted a two equal half-sized countries, their graphs would be the same shape but shifted to the right by a few days. However, they would also reach their "initial" number of cases where the graphs start at a few days later - shifting them left by the same amount! The result would be the same line as the full-sized country.
Good points, but that could be generalized to say that we might as well look only at the worldwide spread. But we look at countries because policies tend to follow those boundaries, so we can see how different choices affect outcome. In the case of the US, we should ignore the national total and look at individual states, because that is where nearly all the policy decisions are made. This might be true of other nations, as well.
There's also this tweet additionally showing how population size of a country has no relationship to pace of disease spread. https://mobile.twitter.com/jburnmurdoch/status/1246185741304...