This seems like two questions.
You will need a visa to enter the U.S. unless you come from a country subject to the Visa Waiver Program (http://travel.state.gov/visa/temp/without/without_1990.html). You will not need a visa to 'flagpole' for Canadian immigration purposes.
The Permanent Resident Card is the best proof of being a P.R. in Canada. You are required to carry a P.R. Card if you travel to Canada by a 'common carrier' (plane, bus, train, boat). If you travel to Canada by a private car, your passport and COPR will be sufficient (but not ideal).