I get asked this all the time (especially at the Miami and Fort Lauderdale Boat Shows) and there is finally a chip that covers all of the Southern U.S., Central and the majority of South America. No need to buy one chip for the northern Caribbean, one for Central America and one for South America, it all comes on one chip. Finally. It's the Navionics NAV+4XG and the coverage is crazy.
Check out the map: https://www.navionics.com/usa/blog/post/navionics-coverage-area-change-for-central-and-south-america