I believe NASA does have a few UHF stations elsewhere, or at least used to. As of a 1998 document about the shuttle program [1], they listed 6 UHF air-to-ground stations, 3 of them in other countries. The U.S.-based ones were in Guam, Hawaii, and Florida; and the others were in Ascension Island (a British dependency halfway between Africa and South America), Bermuda (a British dependency off the east coast of Canada), and Dakar, Senegal.
When someone says "off the coast", I would not expect 850 miles of distance. And, even more, when they say "off the east coast", I would not expect it to be almost directly south of the east coast. Those were the points I was attempting to relay.
[1] http://science.ksc.nasa.gov/shuttle/technology/sts-newsref/s...