I have only imported handguns and handgun parts from Germany so far, so I can't speak from experience on how difficult it is to get grips out of France. I've heard it can be extremely difficult (or impossible) to get certain firearms out of France, but I'd be surprised if it were too tough to have something like grips cleared for export.
As to the rules in the U.S., you would have no problem. However, be aware that if the value of the gun parts/components you are having shipped in a single package exceeds $100 wholesale, you will need to file an ATF Form 6. See 27 C.F.R. § 447.41(c)(2).
I'm assuming you're ordering factory wood grips for a Manurhin MR73. Is that right? If so, have you tried calling Kebco to see if they already have what you want in stock over here?