If it catches on with customers, no doubt American airlines will pick them up. If, say, you could get a ticket to Europe on a european airline on one of these, with more amenities etc. for the same price or less as a 747 ticket on a US airline, which would you go for? They might be pushed to take the dive sooner or later..
Airbus does count American airlines among its general customers too - they may be cautious for now, but if it proves itself they may start to bite.
That said, airlines in Europe and Asia do seem a bit more long-haul orientated versus the US, and so this might suit them better.