Personally, I feel that when speaking of countries and peoples, it is more natural to group them by language and culture than by continental plate. Not least because groping people by continental plate leads to silliness like every country on the Baltic Shield becoming a Baltic country. Completely at odds with the commonly understood use of the term.
Which is why I specified North America as the area covered by the three large coutries.
However, if we do want to throw in Central America and the Caribbean, can we have a Simon Bolivarlike figure, or a process, that unites most of Central America and the Caribbean?
Turning the area into the great power of north America, throwing its weight around with the smaller entities?