Basically, Canada is given 1 spot in the LLWS.
There are divisions set up, 1 in Quebec, 1 in Ontario, 1 in Alberta, 1 in BC, 1 for Prairies, and 1 for the Maritimes. However many teams per division depends on the number of teams registered, not all are the same.
Whichever little league team wins their division and their competition against the other top teams from each division, advances to represent Canada. Historically, BC has had the most success with the amount of times they've represented Canada.
Not all provinces and territories in Canada are little-league affiliated. So to my knowledge, Manitoba is not little-league affiliated.
I don't know why exactly certain areas are little league affiliated while other areas are not in Canada. Perhaps it's a lack of demand; since little league basically functions as a volunteer program\grassroots initiative, maybe there is a lack of volunteers in coaches, umpires, parents, donations for travel, equipment, etc. Maybe certain areas just prefer to keep baseball regional. Again, not really sure why.