No need to be worried. Just have the proper paperwork for entry in to St. Maarten and pay the fee to the airline. Most airlines restrict the number of animals in the cabin, so the earlier you book your cat, the better. Coming back into the USA is no big deal. Cats actually do not need any paperwork at all coming back, although the airline might require something from a vet saying it is healthy enough to travel. We actually just brought a cat back we adotped from St. Martin in May on Jetblue. It was very easy. They didn't even ask to see the paperwork, we had to offer to show them.