It is interesting. I would have imagined the legacies would all have at least a flight to LHR, AMS, CDG and FRA from all their big hubs, even if operated by a partner (i.e. their European 'twin'). AA definitely doesn't even come close though. United and Delta also have their 'gaps' but still seem to have a more complete route network to the major European airports. It's not just ORD either..AA doesn't offer New York to AMS or FRA either.