For an RV the only endorsement required in most provinces is an air brake endorsement in the event the RV has air brakes. That endorsement requirement is also very common in the US. I don't know about reciprocity in the event the endorsement is NOT required by the pertinent US authority. That will again be determined in accordance with the laws of the relevant province(s). Auto slack adjusters do NOT exempt one from the endorsement requirement.
A little research from an authoritative resource will answer your question. It wasn't long ago there was a thread here in which it was postulated that propane must be shut off before crossing the border. That idea was quickly debunked!