The two cities are just over 200km apart, for your information.
Washington has 4 junior teams in Everett Silvertips, Tri-City Americans, Spokane Chiefs, and Seattle Thunderbirds, they already have a rivalry with the Vancouver Giants.
Washington residents can either be Canuck fans or fans of some other team, when some other team comes to Vancouver, those fans will make the trip across the border to see that team. BC residents does the same thing going to Seattle to watch NFL, NBA, and baseball. It works both ways.
Would it be a good thing to have 2 teams 200km apart? I think it would be great, no travelling outside a time zone. West Coast teams don't have it easy those days.