Rockets require cryogenic fuels, workers and large launch complexes. In contrast, Everest is a mere 9km and the first stage of a rocket will take it to something along the lines of 100km at 2000m/s. It is much easier just to throw more fuel in the first stage (or move to the equator) than try and relocate around the relatively smooth surface of Earth.
Florida's air is humid and dense. You get lots of heat gain from that. The density itself matters. Condensation is a huge source of heat. Freezing is another huge source of heat. So you boil off cryogenics and maybe worse. We lost a space shuttle due to a chunk of ice hitting the wing. Falcon 9 rockets need unusually cold filler; if it warms then it expands and won't even fit in the rocket. It probably pours out and gets drained away, the alternative being a rupture.
The USA would do better launching from near Tuscon, Arizona. It's decently high up and dry, which helps keep the cryogenic content cold. We used to do this in fact, before the Mexican embassy complained about defective rockets crashing in Mexico. We chose to move to Florida instead of making a liability payment deal with Mexico.
