Hi there,
I'm Canadian and did my undergrad in politics at a Canadian university (would be roughly 'top five' in domestic rankings – not that rankings are all too significant here compared to the US/UK). I ended up going to the UK for my master's but was admitted to MA programs at Toronto, UBC, and McGill with SSHRC funding for each. To be honest, my impression is that Canadian MA admissions in political science aren't all too competitive to get into, and I think you'd be comparable to applicants at some decent programs - for what it's worth, my own undergrad had a reputable MA program in politics, and even then I knew of students coming in with a GPA similar to yours. Don't worry too much about extra-curriculars and work experience, as those don't seem to be really emphasized in the admissions process – you may be asked to submit a CV, but I'm not sure how closely they look at that, and your statement of purpose will otherwise be focused on your academic interests and objectives. Your internship experience sounds like more than enough either way. You should certainly submit your GRE scores if there's an option to do so (and I think certain programs like UBC require them for international applicants), and make sure to have a good writing sample, as these may help compensate for your low(er) GPA. If you were able to get higher grades in your upper-level courses, that would probably be seen positively as well – and I think Toronto asks for your upper-year GPA specifically on the application form. I imagine the fact you're coming from Michigan would get your file a decent look regardless, especially if you can get some good references from your professors there.
The one thing to consider (and which I'm not sure I can comment on fully, if anyone else on here may know?) is that I'm aware that Canadian programs are sometimes limited in terms of the number of international applicants they can accept – basically, the Department will have a set amount of funding that it can allocate for tuition remission etc. and only a couple 'spots' are allocated for international applicants as a result (for which they'll have to be more competitive than your average domestic applicant). This may be more of an issue for programs that have guaranteed funding for admits (versus say, McGill and Toronto, where MA funding is more scarce in general), and it may also depend on the particular province and how they set international tuition fees – but perhaps someone else on here would have a better idea about those specifics.
Speaking solely in terms of your academic qualifications, given your good GRE scores and the reputation of your undergraduate institution, I would still consider applying to Toronto/McGill/UBC – you'll be up against students with higher GPA's for sure, but your GRE (and Michigan references) might be able to put you on a better footing. Apart from those schools I'd maybe check out Queen's, York, and Ottawa depending on what your interests are – and if you're more interested in policy-oriented programs then it would be worth checking out NPSIA at Carleton, as well as the Munk School at Toronto. But if you're hoping to go back to the US after, it's worth applying to the 'top 3' even if you have doubts, given those departments are a bit more oriented towards American political science than the others in terms of methodological approaches and where they hire their faculty from, and in general they enjoy better name recognition internationally.
Hopefully this helps somewhat, though I'm sure there's others on here who'll be more knowledgeable about Canadian programs – feel free to PM if you have any more questions about the admissions process nonetheless!