From here I’d boot from a rescue usb stick or something and mount the system partitions under it to continue troubleshooting.
If you don’t have one or it doesn’t work, you may be able to get into the system by passing init=/bin/sh
or similar on the kernel cmdline. You’ll get a bare minimum root shell without a login prompt.
He’ll soon be crawling back to negotiations like a bird on its belly, crowing the entire time that whatever idiotic thing he is going to do has brought Canada to heel. Sad. Weak. Trump always chickens out.