The Anopheles mosquitos [1] which spread human malaria are present at some level across about half of the US, but are just not especially abundant here compared to other mosquitos that do not spread malaria.

In fact, of the ~200 mosquito species which occur in the United States, only 12 are known spread any sort of human disease [2].

[1] https://en.wikipedia.org/wiki/Anopheles

[2] https://www.cdc.gov/mosquitoes/about/mosquitoes-in-the-us.ht...