Are you after the physical answer, or the legal one?
Presuming he still physically has his license, and it has an expiry date beyond when he will be renting the car, then he will most likely be able to physically rent a car. If he is pulled over by the police, then he will most likely be able to lie and claim that his license is valid, and he will probably get away with it.
However doing that will be illegal on many levels.
Firstly, when renting a car, part of the rental agreement is that you have a valid drivers license and are legally allowed to drive in the country you'll be driving in. As his license has been suspended he will NOT have a valid license, and will NOT be legally allowed to drive in the US. Thus by renting the car he will be committing fraud.
Next, by actually driving, he will be driving without a license. Most countries (including the US) allow you to drive based on having a valid license in your home country. He does not, thus he will be driving illegally.
When driving without a license, any insurance coverage he has (including the rental car companies (self-)insurance, travel insurance, etc) will be invalidated. He will be fully responsible financially for any accidents he causes, and very probably even if he isn't at fault. If he is involved in an accident you can all but guarantee that they will check on the validity of his home-country license, and not just take it for granted that it's valid.
If he is pulled over by a police officer it's unlikely they will be able to tell that his overseas license is suspended, but if they can then he will definitely be charged, which will not only come with a hefty fine, but will leave him in a very unfortunate position as far as returning his rental car is concerned as they will not let him drive it to return it to the rental company.
So can he rent a car? Yes.
Will he get away with it? Probably.
Will he be breaking countless laws and potentially risking prison time? YES! (Driving without a license in California can lead to up to 6 months prison, I'm presuming other states are similar)