I'm a dual citizen (US/Canada), and I'm starting law school in the US next year, but I seriously considered going to McGill because of the difference in cost. My brother is there, and he intends to work in the US post law-school. Biglaw firms recruit heavily at McGill, especially because they get LLB/BCL degrees. It's not just like getting your medical degree in the Caribbean. I don't really know much about Pakistan, however.
Basically, after doing a lot of research on the subject and talking to a lot of people, I think it just depends what you want to do. You won't even need an LLM to practice, depending on the state. However, if your goal is to get a clerkship or to work at a firm that prizes where you went as opposed to who you are, you might want to reconsider Pakistan. Ultimately, it just depends on your grades, how well you interview, and who you know.