I would consult with an attorney about the contract that you want to sign even if you are considered an independent contractor to make sure that you could not be held responsible. To answer your question, the two companies can have the same name. I would want to know which company owns the trademarks to any products. If the U.S. company owns the marks and did not file internationally then the Canadian company is free to sell in Canada but may have a great deal of difficutly in the U.S. I cannot imagine that one of the companies does not own a trademark. I would retain a lawyer to investigate that issue for you as well.
This information is provided as a public service to provide a general answer and should not be relied upon as legal advice.