Planning on driving to Quebec, crossing at Detroit. Am fully vaccinated and have the booster vaccine (Pfizer)

I talked to US customs and border patrol and they said I need a PCR test , I think they said 3 days prior to entry. I would also need to fill out an app called CanArrive. US CBP said I would have no issues returning to the US.

I plan to cross over into Canada and return the same day. Any US citizen been to Canada recently?

I am a USC but live in Canada. Last Tuesday I went to the US for a few hours, then back to Canada. What you have posted above was true then, but it seems to change very quickly.

FWIW we were waved through the US border (we have NEXUS), no questions asked, all Canada was interested in was ArriveCan.

When the US Border Patrol supervisor told me that all I needed was a negative PCR test no later than 72 hours prior to entry into Canada, I forgot to ask him if that same test was good for US entry, or if I needed another PCR test done in Canada.

You don't need a Covid test to enter the USA via land.

My stepdaughter went to Canada last month to visit her children. She is a US PR.and had to do the same as you have described. No issues on the return to the US from New Brunswick.

I am a dual UK/US citizen and drove into Canada for the day a month or so ago from Buffalo, NY. I did need a PCR test taken within 72 hours, and I did need to fill in a form on the ArriveCAN app, but it was all pretty straightforward. Coming back to the US they only checked my passport, and the car boot. I used a drive through PCR test from CVS and my US passport in both directions.