The Americana focuses particularly on the American continent. Obviously, therefore, it would be the place to look if you want to find information on this continent. It has lots of other material, but not as in depth.
The general encyclopedias, in both the Library of Congress and the Dewey systems, are placed at the very beginning of the collection because they are the most general books in the collection. Go there, in whichever library you are using, and take a good look at the encyclopedias which are available.
Finally, go to the library's catalog and look up the term "encyclopedia." What you will find is that there are an AWFUL lot of encyclopedias in the library, but most of them focus on just one subject area. That brings us to our next subject...
Before you go, however, place encyclopedias firmly in your head, along with almanacs, as one of the first places to look for information. They are incredibly useful; don't forget about them!