Everyone has these problems every once in a while.
Mine: From some recent experiences, MIA comes to mind. Arriving on BA in the early evening meant the immigration lines were rammed. This was after a 15-minute hike from the gate. Then you have to go through the new/idiotic system of entering your details at a kiosk only for it to print out a slip with which you have to stand in another line for 30 minutes to meet with a CBP officer. Then you have to walk another half-marathon to get to the toy train to take you to the car rental center...