This is my opinion only, but as an ESL teacher AND an American, I believe your bilingualism and certified translator skills would be more useful to you in the US than a CELTA certification. A CELTA course, at least in the US, doesn't come cheaply at all, and so you're right to question its value. A good TESL course might serve you better given your exisiting skill sets, and be a much better economic value to you. However, if your move to the US would be the result of other events anyway, you might just consider forgoing any additional certifications and see how far your exisiting qualifications might take you once you're there. If you find that additional certifications would benefit you, there are, naturally, available TESL/CELTA courses there.
Again, just my two cents' worth! Good luck. :)