Graduate / What is the impact of sop (political science) for the approaval of MA? [4]

Hello!

I'm interested in Master programs(political science) in Canada. My department is political science and public administration. My GPA is not very high, and i wonder if i can compensate it by a good sop? What is the proportion of sop during the assessment process? Secondly, my university is one of the best universities in my country(turkey) and it is very difficult to make high grades, so in my sop should i mention the qualities and properties of my university? Lastly, how much shoul i give information about my research interest? Thankssss!!!

p.s.the universities that i'm interested in are U of Toronto,UBC, YORK University,Simon Fraser U.