Your link does not say that Canada has a higher mortality rate than the US for drunk driving. It says that drunk driving is responsible for a slightly higher percentage of motor vehicle fatalities (34% compared to 31%). Given that the US has three times as many traffic fatalities per capita, this means that the US has almost three times the mortality rate for drunk driving as compared to Canada.
Your link does not say that Canada has a higher mortality rate than the US for drunk driving. It says that drunk driving is responsible for a slightly higher percentage of motor vehicle fatalities (34% compared to 31%). Given that the US has three times as many traffic fatalities per capita, this means that the US has almost three times the mortality rate for drunk driving as compared to Canada.