A 3,000 mile road trip on mainly expressways would have minimal wear on your brake pads. Now if you were towing a trailer and did a lot of braking in the mountains, that might wear the pads faster. Otherwise, no the trip didn’t wear out the pads. Either the shop prior to the trip was wrong, the shop at the end of the trip was wrong, you have 4 sticky brake calipers, or you rode across the country with you left foot resting lightly on the brake petal. Choose the one that makes the most sense to you.
If you brake with the same foot as you use on the gas petal, you didn’t have a foot on the brake petal. 4 stickly calipers is not likely at all. The shop at the start of the trip had nothing to gain by telling you the brake pads were good for the trip. The shop at the end of the trip did get you to put on new pads, did they show you the old pads? If yes, are you sure these were the pads from your car? Not substitutes for the purpose of selling a brake job? I don’t trust the shop the did the brake job, but not much you can do about it now.