The president would need to rely on Ottawa to track Chinese and Russian missiles that could come at the U.S. from over the horizon.

Canada has a large airspace that offers the US an important line of sight for the US sensors to shoot down missiles from China and Russia. Moreover, historically, Canada has played a big role in air and missile defence for North America.

Trump has proposed missile defence project called the 'Golden Dome', inspired by Israel's Iron Dome. This initiative marks the US's first foray into space-based weaponry, aiming to protect against long-range missiles through multiple interception methods.