As you are originating in Canada, Canada and USA is considered one continent. You are only allowed 2 stopovers from the continent of commencement, which may be taken all at once or one stop now and another when you return. Note that within USA, a stopover is a connection of more than 4 hours. Second you cannot go to South America and return to the originating continent to continue onwards. You would need to go straight to Europe first and continue to Asia from there.