I think that Canada should leave the drinking age at 19 because it seems to be working. In the US, young people hate having to wait until they turn 21 to be legally allowed to drink. Many times they find other means of getting a hold of alcohol and sometimes act in irresponsible behavior. Being able to drink at a younger age gives them a more mature attitude towards alcohol.
With the way it is now, teenagers don't need to seek out alcohol due to its easy access and availability. Making it harder to get would make them want it more. With how it is now, alcohol is not a big deal. Most young people can easily wait for a few years to drink something many have already tried and all have been around. So, to summarize, it would create the same issues the U.S.A faces.