I've never flown AA from BCN, but have flown them many times from Latin America and once from LHR. At those stations they have provided the US entry documents at check in--usually in a ticket jacket IIRC. Are you sure you weren't given one at BCN before you boarded?
No, AA's IFE isn't great, but I find that the time passes nicely if I bring a book and/or an iPad along. It's not a bad idea to pack them even when flying airlines with superdooper IFE, since failures aren't all that uncommon.
As for the diet coke/coke zero/coke light, isn't it all basically the same garbage? Several shovels of aspartame mixed with various other chemicals? Ugh. I recommend good old water, or springing for a nice nutrient-rich beer or a heart-healthy vino tinto. AA usually carries a decent selection of that stuff.
