Canadian vs U.S. Law Schools (in short):

Similarities:

Law school is pretty stressful and features lots of reading and writing. But, graduates from the most prestigious universities gain highly-valuable network, connections, and credentials. Plus, law school develops highly transferrale skills like conducting detail-oriented research, organizational skills, written and oral advocacy.

Pros of Canadian Law schools:

Canadian law schools cost a lot less than U.S. schools - even for international students, but especially for locals. For e.g., Quebec locals pay 50x less than Harvard locals to attend a law school in Quebec.

Pros of U.S. Law schools:

U.S. law school graduates, especially when practicing in trade hubs like New York, have have access to super-high paying jobs. For e.g., top New York firms pay 10x as much as top Canadian firms for their first-year associates. 

U.S. law school graduates also have access to highly influential decision-making positions. The U.S. features more lawyers in Congress and Senate than Canada does in its equivalent chambers. U.S. policy has wider influence than Canadian policy. Last, the New York Bar is one of the best bars to hold to understand and influence international business practice. 

Differences in Recommendations

80K's career page recommends students who have a clear vision of what they want to do, have a high stress tolerance, and a good personal fit for lawyering. This advice ensures that the time, money, and energy that goes into law school is well spent. 

Since Canadian law schools cost less, Canadian law school can be for students who are still trying to figure out their career path since it provides highly transferrable skills and good career capital. 

That said,  unless they can move to the U.S., Canadian students looking to earn-to-give have better prospects in other careers or the U.S.

Canadian law school can be for students looking to influence global change or policy-making, but they'll face a steeper hill than U.S. law students since their credentials are less recognized than the U.S.' credentials (especially within the U.S.).

Why doesn't EA have many career opportunities or recommendations for law students (especially outside the U.S.)?

Three reasons:

1. Lawyering is highly-specific. Lawyers can do three things no one else can: notarize documents, provide legal advice, and become judges. All the other work - policy-making, legal research, and advocacy - can be done by others with enough motivation, organization, and search-engine savvy. As such, most of the work lawyers could be done without the cost, stress, and time of going to law school. As such, 80K sparsely recommends it, let alone tailors careers to that skillset.  
2. Lawyering is problem-responsive. Budding organizations past the start-up stage - like the EA community - have little need for lawyers if they're not running into legal issues. It makes more sense for most mid-sized organizations to hire lawyers as needed instead of hiring them in-house. Only the largest EA Orgs, like Open Phil or CEA, find a regular need for lawyers. 
3. Lawyering is geographically constrained. Lawyers are licenced in specific jurisdictions, creating an institutional barrier to in-depth collaboration. Legal professionals and academics that do collaborate either work on broad, sweeping analyses that day-to-day organizations are still figuring out how to implement, or they work on re-orienting cultural motherships over years of concentrated effort. These problems are hardly tractable (drawing little 80K attention), but their nature is unlikely to change.