That would be a resounding NO!
Look at the issue closely and see the actual figures of the effectiveness of the system have been far from anything to spend further money on.
Of all the tests so far conducted less then 10% have done what they have sought to achieve - downing an incoming missile. 10% for missiles they know are coming, at what speed, and altitude!
Now for the costs... early estimates range from 200 billion dollars all the way up to 1 trillion dollars! Already the Americans have spent over $120 billion and still have very little to show for it. How are we to take part in that when we cannot even fund our health care system and maintain our own aging military? Beyond that, how much input into the process are we really going to get in the whole ordeal? Without doubt, very little in fact.
Moreover, look at the connections between the current American government and those that have been contracted to build and maintain the missile systems. The connections are dubious to say the least.
Now, do some research of the potential enemies. Russia and China have both openly said that the missile defense system as proposed by Washington is no deterrence to them because they will simply build more missiles, with more warheads and include with them more counter measures. No amount of money spent on missile defense could stop them.
Offense in this case is far cheaper and easier to deploy then defense.
As for rogue nations - why should they launch a multi-million dollar missile to attack America when it was clearly shown by Osama Bin Laden that a few determined men could inflict massive casualties with just a little planning. No missile defense system can stop a dirty bomb or suitcase nuke. Who really thinks the bad guys are going to play by the rules?
Missile defense is nothing more then a scam to give false hope and to line the pockets of the military industrial complex in the United States. It will cause a new arms race, which we had just turned away from. Remember now it took the US pulling out of the long established Anti-Ballistic Missile Treaty to get their plans this far.
We should focus and concentrate on preventing new threats from emerging in the first place. Canada should avoid this little fiasco and spend the money where it is really needed, here at home.