There’s climate, too. Look at IL in USA. Cases & fatalities low through summer, with one of the stronger (although in my opinion quite flawed) mitigation suites in the US. Fall hit, and good God.
I think another difference is that in the US, not only did the virus get a good foothold before mitigation cut in, but we have a large contingent of the populace who mitigate poorly (mask over mouth but not nose - let’s see who can attain orbit with a sneeze), and another that rejects it entirely. I guess in the pond analogy, one would say “too late, and too few carp”.
Hey. I mitigate poorly and am proud of it. I breath in through my nose, which is left uncovered, so no microbes can escape that way, and out through my mouth. And this old Japanese guy makes me polish all his cars and says he’s teaching me Karate.
Can’t cover the nose, because after a while the masks smells like somebody’s a$$hole, and dying of that is more likely than getting Covid or giving it to anyone else.
Sneezing is what the inside of the elbow is made for.