The president would have to rely on his “51st state” to track Chinese and Russian missiles that could come at the U.S. from over the horizon.

US President Donald Trump has announced big plans for a powerful air and missile defence shield across North America. But he can’t build it without Canada, and it’s still not clear if Canada wants to be part of it,

Canada is in talks with the U.S. about President Donald Trump's proposed "Golden Dome" missile defence plan, the Prime Minister's Office confirmed Tuesday, shortly after Trump claimed Canada "has called us and they want to be a part of it.