It's different if you just drive through. No overnight. I've been hassled in minor ways coming back to the US (never hassled when entering Canada), expired passport, and (different entry) used the Nexus lane without a Nexus card. Grand total delay, maybe 3 minutes. I'm CCW and life NRA, registered republican.
That said, one is dealing with the government, and such a deal is inherently irrational and unpredictable.
Oh, do NOT attempt entering Canada if you or anybody traveling with you has ever had a DUI/DWI.