Question re: US vehicle registration required for crossing borders in CA and South America?

Hello, here is a post for anybody who can still remember life before the pandemic and/or can still imagine a post-pandemic future (maybe next year?) where it will be possible to drive the americas without being overwhelmed by fallout from the pandemic.

We have a US vehicle with title in our name but would like to know if it is also important or not to have valid uptodate US vehicle registration and/or US vehicle insurance when attempting to cross borders (temporarily import) in a US-titled vehicle between countries in CA and South America?

We would also like to hear from anybody who has a magic bullet to stop COVID-19 pandemic and wipe out all side effects of pandemic on driving the americas - but suspect this may require a bit more time and patience (-: