Upvote:2
Officially one of the requirements to enter the US using the Visa Waiver Program is that you are "in possession of a round-trip transportation ticket". This previous answer includes links to the specific legislation that covers this requirements and includes further details on the exact requirements.
Given your specific circumstances it's likely that US immigration would allow your entry, however your issue will not be with US immigration, but with your airline.
Enforcement of the "return ticket" requirement is carried out by the airline that carries you to the US. They have a legal obligation to confirm that you meet certain criteria before they are allowed let you board the flight - and a return ticket is one of those conditions.
Realistically I don't believe anyone other than possibly the airline will be able to give you a definitive answer as to whether they will allow you board the flight to the US. By the letter of the law, it's a clear-cut 'no', however it's possible they will make an exception based on your Canadian PR - but officially doing so leaves them open to being fined by the US Government for allowing you board a flight without meeting the VWP requirements.