Just to add to this if your instance(sh.itjust.works) want to block lemmy.ca cause the those Canadians are the worse then you won’t see their communities. You can sign in on lemmy.world where they have not block/defederate Lemmy.ca see the posts there.
Most of the time the instance will block/defederate other instances to protect their communities/members. Like if Lemmy.ca asked Lemmy.notCa to control their maple-deniers members that posts “Maple syrup is a hoax”, and Lemmy.notCa refused, the Lemmy.ca can defederate/block Lemmy.notCa.