As a former PD, a few years ago, I was approached by one of our interventional cardiologist who wanted us to look at a FMG candidate. While having someone advocate for you may get you an interview (that is if your CV/step scores are acceptable), it is still the makeup of your ERAS packet that will secure your position. Given three identical candidates except one is US allopathic, one is DO, the other is FMG, the likely ranking would also be in that order...not trying to be disagreeable, just telling you that when the rank meetings are held, the people making the decisions may not give a damn about the personal letter of recommendation, as was the case with the cardiologist's man, the chair nor vice chair cared. There of course are exceptions, there was for a very strong candidate who had done 2 prelim years and we had an opening in the pgy 3 class; this man was an FMG that had done heavy duty research and a power chair of surgery called in for him. So anything is possible...
FYI- Realize also that this past year, due to the number of new med school positions (MD and DO), that there were actually more US med school graduates than residency program positions (FP, Medicine, Surgery, etc) in the US.
Best of luck!