Escott Reid, an important Canadian diplomat involved in the formation of NATO (North Atlantic Treaty Association) believed that creating such an alliance would be of benefit to Canada as it would pose as a convenient solution to his country's concerns.
He wanted the US to join to serve as a link to its trade partners and provide potential economic advantage to Canada.
The one disadvantage for the US to join NATO is the duty to defend the other members of the alliance in any case of conflict.