Why do US based airlines suck so bad?

So I recently traveled from Atlanta to Dublin. We flew with Aer Lingus and the flight was great. So I got back to the US yesterdays and had a short connection in Atlanta. I thought to myself based on the great service Aer Lingus gave me my short flight shouldn't be too bad right? I was sadly mistaken. The flight was an hour delayed, the flight staff were rude. They served snacks, but the prices were outrageous and the selection was awful. It was an awful experience. Compared to Aer Lingus, this flight was like being in a concentration camp. I know it's a short flight but it could have been a lot better. I'm also not someone to complain a lot, but US airlines don't even come close to the top airlines in Europe. What's the main cause of US airlines sucking so bad?