I cannot see why one could not do a standalone FAA PPL/IR in a turboprop.
Under 12500lb, no Type Rating is required under FAA rules unless specifically required (any such cases?) or it is a turboJET which this isn't.
The practicalities will be something else. One would start flying on a U.S. Student Pilot Certificate and one's solo flights would be done on that. Legalities aside, I would do some serious "due diligence" before going down this route because one could find not many instructors / schools are willing to do this.
However, in the USA, one can do one's PPL/IR (or even an ATP) totally with freelance instructors and examiners, and that would probably be the preferred route in this case. OTOH that isn't going to be so easy to arrange for a European going to the USA, where he starts off knowing exactly nobody...
Here in the UK, I looked into (for no particular reason) the possibility of doing a PPL in a TB20 (a "complex" piston single!) and no school would touch it with a bargepole. OTOH there are schools elsewhere in the world which teach the PPL in TB20s, and there is nothing difficult about it.
Practically, there is going to be a helluva learning curve compared to doing it in a Cessna 150
