With motor and transmission installed, running or not, it cannot be legally exported to the US.
100% disassembled, without a drivetrain, it "might" (M-I-G-H-T) be able to be legally imported in to the US.
If the motor and transmission are in the same shipment, the car cannot be legally imported in to the US.
Trans Canada will be more of a pain to deal with than US Customs if the car is 100% disassembled and ship to the US as "parts".......
That is the bottom line.
Bill S.