According to NAFTA (North American Free Trade Act) any good made in the USA or Canada are duty free.
Any goods manufactured in the USA are free of duty regardless of which country they are coming from.
If the person importing the items purchased them for his/her own personal use they may be entered with an informal entry. Generally a single sheet of paper, sometimes just a wave of the hand. Without the payment of duties or fees.
If the person importing is bringing the machine in for sale or resale and is valued over $2500 USD then the officer can and generally does require a formal entry, which generally needs a Customs Broker. The Customs Broker will do the necessary paper work for a fee. This fee will vary from broker to broker. Plus there is a $10 fee for the vehicle carrying the machine.
So if I go to Canada and buy a Stern/Bally/JJP - etc -machine and import it for my own personal use. A simple one piece of paper is about all that is needed.
If I go to Canada and buy the same machine that is over $2500 in value and intend on selling it or putting it in my bar, then a formal entry is required. Still no duty, but a broker's fee.
That is for the Federal side of things. Whether the state you are importing to, taxes purchases in Canada is beyond my knowledge
Also if you are carrying over $10,000 in cash or other negotiable instruments you MUST report the import and export of the funds. I think Canada has the same requirements.