I have a friend who is staying with me in California for a few days. He is a German guy who bought a car in Canada about a year ago and he drove down to the US. He's been driving a while and I am his last stop before he heads into Mexico. As he was preparing to head to the border he realized in shock that his registration had fallen out of a packet where he kept it. There had been some ride sharing with some people and the packet was used to keep some other docs. Well, he was both sure that it had been there and equally sure it no longer was. A call to the ride share friends at their home in LA confirmed that they didn't have it.
I told him what he knew - that there was no way he could cross into Mexico without it. You need to get a permit from the Mexican Govt to go anywhere outside of Baja and it absolutely requires a valid reg card.
I was sure he was fairly screwed. Having dealt with the DMV in both California and NY when I was younger I told him he should start thinking about skipping the Mexico leg of his road trip.
Check below the fold to see how Canada helped him out.