The FAA could care less about your paperwork. They will only accept a fedfax from transport Canada, which is the ancient telex system that is secure. The cleanest way to do it is have an escrow company handle it, well worth the fee. You also need either the hard copy US registration or what is termed a flywire confirmation for international flights. Lately, the escrow company has gotten me the hard copy in a day or two, flywire in 12 hours. You also must have a customs decal, or the receipt copy of the application showing the fee paid confirmation. It can take as long as 6 weeks to get the actual decal, unless you request expedited handling. Your customs broker can do the SID, Standard Import Declaration. There is no duty on aircraft, but you may still have to pay for the customs bond fee.
Just finished up my 206H from India off the boat yesterday, leaves the port today heading up the hill to Flagstaff. My other Caravan in India just got deregistered so I am in the process of doing the paperwork packet. You may have the issue, kind of a technical crunch one. The CofA is not valid without the Canadian registration, well kind of maybe, since we have a reciprocal agreement with Canada. However you best ask your local International Flight Standards Office (I do not know which region has Canada at the moment) if you must do a 8130-6 Application for Airworthiness Certificate (used for ferry flights now). Cleanest way, have the seller or a designee fly it to the US, then do all the BS paperwork once it is sitting on your ramp. These little issues, like the CofA validity can have big issues if there is an insurance claim, like they will not pay. Oh, there is other little issues that may crop up. You would need an FCC Radio Station License for the aircraft to be in Canada with a US registration, normally they don't check, but since you will be between universes, so to speak, they may actually look. Hopefully you still have your Radio Telephone Operators Permit, rest of the world requirement. There is the DEA requirement of the little placard by the tail, getting the C number off and putting on a N number and so on.
Bottom line: have them fly it down, then do the paperwork. Hire an escrow company, International is a bit messy. Sure you can do it yourself, like that Russian doctor that took out his own appendix in Antartica, possible by why risk it.
My travel paper crap packets for the trip to India to fetch the Caravan:
