Air mass is defined as the mass of the huge body of air which develops over a specific region over time. Tropical warm air mass forms over the tropical area which is near to equator.
Miami, Florida lie closest to the equator, thus, it is most affected by tropical warm air mass.
Since, other three i.e. Charlotte, North Carolina; New York City, New York; Denver, Colorado are not closest to the equator. Thus, they are not most affected by the tropical warm air mass.
