What common social practice(s) in modern economies like Canada resemble (s) the Potlatch?
There is very little in modern economies that resembles the potlatch. The potlatch was a means of redistributing wealth and of acquiring social status. A person would hold a feast, give away lots of goods and food, and thereby be seen as a wealthy and influential individual.
One could argue that weddings are the social practice that most closely resembles the potlatch, though they are somewhat different. At a wedding, the parents of the couple provide lavish festivities. They may hope to show their wealth and taste by doing so. However, these affairs differ from potlatches because the guests reciprocate on the spot by bringing gifts. In a sense, both sides at a wedding are redistributing wealth and both sides are trying to gain status by showing how much they can afford to give.
True potlatch-style events are not really possible in a modern economy because the economy consists of so many more people and so wealth cannot truly be redistributed simply through the actions of individuals. The things that do resemble potlatches resemble them more because they show the pursuit of social status.