Importation into the US is fairly easy...especially if the aircraft is fairly stock.
The place to start is the Type Certificate (TC). Be sure that any equipment on the plane such as engine, props, floats, wheels, etc listed on the Type Certificate are actually on the plane and that any deviations to the TC are are validated by an STC. Don't make the mistake of thinking that just because all the 185s you have seen have 8.50 tires, that they are on the Type Certificate...do your homework with this kind of stuff.
Aircraft in Canada are required to have four logs...the journey log, airframe log, engine log, and prop log. Any major repairs or modifications must be detailed in the journey log but the other logs will have all the real information such as parts trace-ability, design or repair approval numbers, STCs and so on. STCs may be incorporated by reference in the appropriate log book but the STC paper work itself is most often included in the log.
Don't get excited if you see a few different methods of log/record keeping for various aircraft. Transport Canada approves various procedures for logs/record keeping for commercial air carriers so if you see some different record keeping methods it's not a big deal. Continuity in the dates/information is what you really need...not continuity in the methods used to keep logs/records.
The US accepts the the information in the Canadian Logs because they meet ICAO standards and, although it's a slightly different way of doing things, the FAA is obligated to accept the format (maybe not all the content though) of these logs as an ICAO member themselves.
Canadian Aviation Regulation Standard 571 Appendix L - Major Repair or Major Modification Report details that major repairs or modifications be reported to Transport Canada ("the Minister"). Ideally you should see a copy of this report with a corresponding entry in the log book. Unfortunately though, there is no Regulation requiring the owner to keep these records and Transport Canada's data base is not always complete.
Finally, if the airplane was registered in the US before coming to Canada, any work conducted in the US using an FAA 337 is accepted in Canada unless it originates from Alaska. So if the records for the Canadian plane you are looking at has 337 forms, don't get worked up. Unless they come from Alaska... because I understand the FAA will not accept Alaskan 337s in the lower 48...(maybe somebody could set me straight on that)...337s are accepted here and, while not a Canadian document, they may form part of the aircraft's Canadian Logs. However...if old US logs show work done without a 337 or STC there is a problem. The 337s should have come with the plane but sometimes airplanes are imported into Canada without them under a "condition inspection" process...you don't want to go down that road $$$$$.
Short Answer...if the plane conforms to the TC and/or has supporting STCs or major repair approvals if required; you should have no issues importing a plane from Canada into the US. It's done all the time.