It's not that hard to get a rough idea.
List of counties in California - Wikipedia
80% of the population is concentrated in counties making up 35% of the land area, and much of the space in several of the larger counties is largely unoccupied mountains or desert (e.g. San Bernardino, San Diego, Riverside, Fresno).
Those facts speak for themselves, what the problem is is the definition of "unpopulated". Is it "Not another person for 1 mile.", "Not another person for 10 miles.", "Not another person for 20 miles.", "Not another person for 30 miles.", "Not another person for 40 miles.", "Not another person for 50 miles.", "Not another person for 100 miles.", or what.
With California being approximately 220 miles wide and 770 miles top to bottom, I'm pretty sure that it wouldn't be the last one. With Canada being approximately 5,780 miles wide and approximately 2,879 miles top to bottom, the second one could well be the one used.
But that's only a minor point, as I don't really think that density is as big an issue as people make it out to be when making excuses for Spain and Italy, for instance, especially when the populations are generally implementing social distancing.
When you compare equivalent areas (for example Vancouver BC [pop.dens 5,493/sq.mi.] and Boston MA [pop.dens 5,396/sq.mi.]) you can get a better picture. But I've run out of excuses not to run errands so I'll have to leave you to compare the cases and deaths between those two cities.
You haven't given any reason to conclude that it's relevant at all, ...
I am well aware that "correlation" and "causation" do not mean the same thing.
...much less that there should be a 100% correlation as you've reflected in your calculation.
No, that is true, I did not "give a reason" why the numbers should correlate. I also don't "give a reason" why water is wet.
So what? Different states/countries have been hit at different times, and it usually takes an actual imminent and local threat for people to react. Most of the June/July spike in the US was driven by states that were having their FIRST spike in cases during that timeframe, not their second.
Incidentally, Spain, France, Italy, the UK and Germany (which you apparently think have such better leaders than the US) are all showing signs of heading into a second peak. Only time will tell.
I deal in concrete numbers. I do not deal in "historical patterns". The people who do deal in "historical patterns" have been unanimous that there would be MORE than one "wave" (they do, however, differ on the number and severity of the successive waves).
Also, you're ignoring other important factors, like the fact that several of the countries you listed have a much higher general level of individual discipline than the US (e.g. Japan, Germany), and the presence of significant risk factors in the US, like obesity and income inequality, which are not as prevalent in the other countries you listed.
If you can give me solidly quantified data on "general level of individual discipline" and the other factors you cite, I'd be more than happy to consider them.
However, I do have to admit that I am not set up to do "multi-value analysis" of the nature that you feel is absolutely essential before concluding that the US is NOT doing as well as many other countries are doing in fighting COVID-19.
What you appear to actually want to debate is exactly the gender makeup of the equine excrement that the US is in WITHOUT admitting that the US is actually in any equine excrement at all.