I'm by no means an economic expert (I did Politics for chrissake!) but I would imagine that, seeing as Boeing's business is global in that a large proportion of their components come from abroad, the weak dollar is hurting them as much as it is 'hurting' Airbus.
I think Boeing are hoping for the majority of 7E7 orders from the US market, after all theirs is the most optimised for such a size of aircraft and it's where the majority of the early model 757/767s are approaching retirement.
Those bleedless Trent 1000s are going to be very expensive in dollar terms for US airlines if the greenback falls further.