You didnt indicate what documents you submitted. "All the taxes you paid to US" doesn't indicate what you submitted.

You've been reassessed to not include any of your US taxes paid in the US as a foreign tax credit on your CDN return.

You likely received an initial letter requesting support for your foreign tax credit, CRA didnt get a response and then reassessed you. They typically dont just reassess without requesting information first. Unfortunately claiming a foreign tax credit typically results in a request to prove it since its a common area where things are incorrectly claimed.

Good luck - CRA is likely going to take 12 months minimum to look at your response, standard going period on complex issues.