Unlike The Stick of Truth, Canada is only slightly present as an Easter egg in the South Park sequel. It's not that easy to find it either, so here's where to find it in The Fractured But Whole.
When you arrive at the organic foods vendor, he'll move in front of you, blocking the way that leads to the Canadian border. To get past him, you need to pick up a basket of Memberberries and use it to block his path.
Once you do so, you'll find the Canadian border via a short cutscene. Unfortunately, there is no gameplay involved with this Easter egg once you pass the vendor. Hopefully, a separate Canada DLC will come out soon enough and fill in the gap.