I do believe this may be getting just a wee too far fetched.
A disgruntled Captain who is leaving isn't very likely to be the most reliable source of information, even though I have to admit that there are many unhappy crew in SIA at the moment who have been treated very badly and all with the full endorsement of LKY.
All that said I also believe that SIA's maintenance procedures as as good as anyone else and I do doubt very much that the FAA would be objecting to the presence of SIA in American airspace.
Long before they can do that they have to mend their fences at home.