From a customer experience/user experience standpoint, shopping inside an airport can be tricky for the customer. There is dwell time at the beginning of a trip -- the most favorable time for shopping, but the least favorable time for taking away one's purchases. Customers find themselves considering items not simply for their appeal, but for whether they will fit into a carry on, add bulk to suitcases, etc. Many passengers are avoiding baggage fees by loading up their carry-ons, leaving little room for purchases and making shopping difficult while they lug those suitcases around.
Some customers might consider buying an item on the return trip, but that's the least favorable time for the retailer to earn their business -- after the travel money is spent and the customer wants to get home.
To me, this seems like a good opportunity for BOPIS in reverse -- "Buy in store, ship it to me." Some have tried at this and failed. For that to work, the retailers need a strong store staff to create and execute on an experience designed for the airport customer. To answer the question, I do believe the offerings at U.S airports could be improved, so long as they are backed by the execution of great service inside the retail stores. High-end stores won't compensate for mediocre service.