The reason we have very few cases of malaria in the US (as I heard when an entomologist/mosquito expert gave a talk) is that we have air conditioners and tend to be indoors when most of the malaria-carrying mosquitoes are out and about. Our lifestyles aren't conducive to the spreading of malaria. There are a few cases every year, though, about 15.
” that we have air conditioners and tend to be indoors when most of the malaria-carrying mosquitoes are out and about”
Most importantly, mosquitos aren’t born with Malaria. They have to have a blood meal from someone who already is already infected. The way yellow fever were eliminated when we built the panama canal was to first eradicate all the mosquitos which were capable of carrying yellow fever (only certain types can carry it). Once we eliminated the mosquitos then the yellow fever disease disappeared. After that, the mosquitos only had to be controlled since there were no yellow fever sufferers around to contaminate the mosquitos. Since mosquitos have a very small range I’m not sure how Malaria could be spread in US unless the 15 cases you mentioned are mostly contained in a very small area and contain an individual who is a carrier from a previous contamination. I think a person who has had malaria carries it for the rest of their lives. That is true in some types of malaria, anyway.