When launching rockets, you generally want two things:
1. Open ocean east from your site, because launching to the east adds velocity - this is the direction in which the Earth rotates, so free speed for you; and ocean is better than land, because no one lives on the ocean and the nearby waters can be closed during launches. If you launch over the sea and anything goes wrong with your rocket during ascent, at least it won't crash on anybody's head and home.
(Russians can afford launching over land, because the steppe is thinly populated and they had no qualms removing the nomads from around Baikonur.)
2. To be as close to equator as possible, because the boost that you get from Earth's rotation is multiplied by cosine of your latitude.
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That is why the French are so happy to have French Guyana. In the contiguous U.S., you only have two states that are suitable: Florida and Texas, both pretty far south and with open sea east of them. That is why the Kennedy Space Center is in Florida.
But real estate in Florida is more expensive than that in Texas and building a new cosmic base there would not only cost money, but bring hassle with the locals because it means sonic booms in the proximity of cities and villages.
Boca Chica is ideally suited for this purpose, fairly cheap land and not much population to speak of.