Can a Canadian company sue an American company for this? Which country would have jurisdiction?
No one is going to be sued, not is anyone doing anything illegal in this case.
For example, in all US jurisdictions it would be illegal for a business to say, “I am not going to serve you because you are black” and in some jurisdictions it would be illegal for a business to say, “I am not going to serve you because you are gay.”
However, in this case, the organization that is being denied service is being denied service due to its position on some political issue.
The Pro Life Group has no case!
That is unless you would want to be be sued for refusing to rent a piece a property that you owned to Planned Parenthood.