The cold weather places in the US don’t have mosquitoes during cold months, but my experience is there are tons of mosquitoes in those states once it warms up, and those states seem to be more hesitant to kill them. In FL we spray and drop pesticides into the lakes to reduce the mosquito population. I have more trouble with mosquitoes in Michigan in July than I do when I’m in Florida.
Although, some parts of Florida are more aggressive about it than others. Where I live now everyone is older, and I think the city doesn’t worry about us getting cancer from pesticides because we are close to death anyway.