Summer leisure demand into BCN from northern Europe is aggressive. Transatlantic nonstops exist but are thinner than London or Paris; many US tickets still connect in Lisbon, Madrid, Amsterdam or a Gulf hub depending on the westbound wind and the airline.
El Prat
Two main terminals. Connections that change terminal with checked bags need more time than the “T1 to T1” ones. Vueling, Iberia, Level and a mix of Gulf and transatlantic carriers share the campus; they do not share ground handlers in a way you should care about, but you should care about the terminal on the boarding pass.
Cruise and city
If you are joining a ship, the arrival hour matters more than saving €40. A 21:00 inbound the night before embarkation is a quote we will defend. A 11:00 inbound on sailing day is a quote we will argue against.
Open-jaw Spain
BCN in, MAD or AGP out is a normal pattern. Multi-city pricing usually beats two cheap one-ways once you want bags checked through.