You can apply for a US visa in any country in the world where there is a consulate or embassy where you can attend for the interview.
Being a PR is only part of the application and guarantees nothing, your nationality/passport is the main consideration as far as a US visa assessment is concerned as well of course as purpose of visit. Of course better to be a landed PR than not and to have a Canadian residential address.
Until you have undergone the landing procedure at either a Port of Entry or at an IRCC office, you remain a "Foreign National". The simple possession of the visa/COPR do not affect your status. The USA will assess your eligibility based on your current status.