US would definitely benefit by taking some belugas, new blood is desperately needed. But there are some problems. First of all, most of the animals are wild caught so getting the import permits will be not easy. In addition, many animals might not be healhty, introducing sick animals in a healthy population might not be a great idea, and getting new aninals that might died with a couple of months would couse bad publicity and criticism. There is also an issue with space, all of the SW, Shedd and georgia are almost overcrowed. Mytic has some space aveilable but I dunno that they´ll be willyng to accept more MLC animals after the death of the three belugas.
Maybe US could accept some healthy individuals, as BlobfishBoy already said, but I can see most of the animals being sent to Asia, specially China.