No surprise that USA and Canada dominate the Americas. They are popular with collectors and the themes resonate all over the world.
“Latin America” is not accessible or available to the same extent in the English-speaking world. Over the last year or so, I have added a lot of stamps from Central and South America.
I am not a big fan of the “island” nations and those quasi-British issues such as “Royal Visits” and “Royal Weddings”. They are however much more available than mainland Central and South America.