As a US licensed and trained pilot, I know I can fly into Canada, but are there are airspace rules that are different from the American system. Is there a Canadian rules test or conversion you can or should do, or should I just expect to fly in Canada by the exact same rules and procedures as in the United States?
In the specific case of Canada, AOPA and COPA have a lot of information aimed at US pilots. AOPA has a complete guide on documents, customs etc. and COPA has a page with more information, which includes this remark:
The flying rules are almost indistinguishable - reading the COPA guide should keep you legal and out of trouble. Make sure you get a Canada Flight Supplement (CFS) and some VNCs (Canadian equivalent to your US sectionals), that will allow you to navigate VFR safely. IFR plates are available from Nav Canada as a subscription or the (sample list of) vendors included below. (by mail order)
The guide is free but available to AOPA/COPA members only.
No, you need to know the differences.
A big one is all airspace between 12500 and 18000ft is Class B.
So you need either an IFR or VFR clearance.
Class B airspace is any controlled airspace between 12,500 ft (3,800 m) and 18,000 ft (5,500 m) Occasionally, Class B airspace exists in other locations, though this is unusual.
Class B Controlled low-level airspace (above 12 500 ft ASL, up to 18 000 ft ASL); IFR and CVFR only.