Three years is a ludicrous impossibility, which is why "we must have capability in three years" = "buy P-8s".
If Airbus, Kawasaki, Alenia, and Lockheed can't do it in three years, then what is so special about Boeing that they can? In my opinion, if the former can't do it, neither can the latter. Conversely, if the latter can do it, then the former should be able to as well. I personally don't see the P-8 or its manufacturer possessing anything special in this arena.