Also at the US border, they are going to ask for your status in Canada and you will have to show them your PR card, that could be a problem as well ...
And at the US Border, what are you supposed to tell if they ask for your Canadian PR card (they ask for it everytime) ?
Tell the truth.
Possession of a valid PR card is not a requirement for entering the U.S.
The U.S. border officer can ask a traveler about status in Canada, and can ask to see a status document showing that status. However, not every crossing will entail this line of inquiry. The actual line of inquiry, on any given occasion, will vary widely and depend on a range of factors. Travelers who have crossed using that same PoE before, and particularly those who have done so multiple times within the relatively recent past, are less likely to be asked probing questions. Many times a simple, truthful response to a question about status in Canada, as in "I am a Canadian Permanent Resident," suffices with little or no follow-up.
If the U.S. officer asks for a PR card, the traveler should produce it if the traveler does possess it. Valid or expired should not matter, but if it is expired that could lead to some additional questions. No big deal. Just answer the questions honestly.
Ultimately how it goes at the border will depend on the traveler's status to enter and be in the U.S. Questions about Canadian status are merely relevant to assessing who the traveler is, what the traveler's intentions are, and whether the traveler will comply with U.S. immigration and other laws.
Sure, if there are some doubts about the traveler's status to return to Canada, that could influence a U.S. border officer's concerns about the traveler potentially overstaying in the U.S. Which in turn could lead to being denied entry into the U.S. For the vast majority of Canadian PRs there should be little or no reason for the U.S. officers to have such concerns, even if the PR's PR card has expired, unless there are indeed circumstances suggesting reason for such concerns.
All this warrants the caveat that the U.S. side of the border tends to be more difficult for some travelers depending on some well-known (albeit abhorrent) discriminatory biases. Unfortunately.
