A few years back a close friend broke her foot and could not drive. She had business in California and asked if I would drive her van from Iowa to the Bay area, at her expense, plus a little compensation. She spoke with her insurance company and her father, a retired Kansas Sheriff, and came up with a packet of documents. One was a letter of authorization for me to drive, proof of insurance coverage on her policy with my name and drivers license, a travel authorization from Des Moines to San Francisco, a copy of the current registration, a copy of the Title to the vehicle and a current inspection for vehicle safety. Sounds like a lot of paper, but covered all possible problems I might have. When I returned, I had the same packet for that trip. It took a while to put together, but there was no doubt I was legal. If I was stopped in Connecticut, there might have been some issues. We did this because the van was loaded with about a half million worth of rare books.
With an international/non-resident license, you should take as much precaution as the owner, his insurance company, and the states you travel in recommend. But legally, you can easily meet the necessary regulations to have a safe trip.