In case someone requires this in future.....I am sure lot of H1b will move back to US. They would want to import their cars back.
If you bought the car in Canada
1.Contact your manufacturer and get two letters with your VIN number mentioned in it.
-That your car meets the EPA and Federal Safety Standards.
-There are no pending recalls.
2.Now the tricky part .....TPMS. TPMS is mandatory of cars sold in US (not sure when this became mandatory). If your car is equipped with TPMS then nothing more to do. If not......then if you go according to book, you need to bring your car up to the Federal Standards installing the TPMS through dealership. Get the invoice and present it during the importation. Not to mention this is very expensive....my estimate was 3500 CAD.
Cheaper option is buy external TPMS and install it yourself. Now I heard mixed success with this option......depends upon the officer you encounter. He may not like it...he may not care......anything is possible.
3. Fill up two forms one DOT HS7 and EPA 3520. Take along or they will give you at the border. There are few options where you need to fill up the form properly. I had so many questions, the officer looked irritated. Finally said no need to fill those, just fill the custom entry form 7501. This is main form, get at least 2 original copies of this with original stamp. Need to submit this form to DMV along with Canadian registration to get the title.
Also make sure entry form 7501 states that the car meets all the necessary EPA and Federal Safety regulations.
4. Nothing needs to be done on the Canadian CBSA side. Directly drive to US CBP side tell the officer at the booth you need to import the car.
5. No tax was charged as the car manufactured in Canada and I owned it for while.