I'm not sure what you are referring to by "syllabus". FMGS or American grad, they all take the EXACT same USMLE. There are not different versions for different applicants, only different forms which are spread amongst all takers, not just between AMGs and FMGs.
Rumor has had it that FMGs received more difficult exams (probably trying to account for the less impressive pass rate of FMGS compared to US grads) but this is false. No difference in difficulty for the two groups.
Hope this helps.