Maybe the Canadian Prime Minister would have said "yes", if there was just one successful test with the system. It even failed in unrealistic scenarios with gps-transmitting missiles to be intercepted.
When will it work or will it ever work? That's the important questions.
I think Donald Rumsfeld best addressed this issue:
DR: "I think the word "deploying" needs to be calibrated. What's being done here is not a pure test and not a pure deployment, but deploying the pieces of the capability that will evolve into an early missile defense capability, and the way to do that, according to the people who are working on this -- and I agree and subscribe to the concept -- is to get it in the ground in a modest way, work the problems, keep testing, and as that capability evolves, you will begin to have the early stages of a missile defense capability. If you didn't do anything until you could do everything, you probably wouldn't do anything."