Is there a way to determine which items are children of another item?
 
For Example, if my hierarchy has the following structure:
World
 - Americas
 - - USA
 - - Canada 
 - Europe
 - - UK
 - - Ireland
Is there an association I can use as a lookup to determine this relationship in another list or module?  For example, I select America and I can determine that the first child is USA and second is Canada?
 
I thought about trying to do this inside a numbered list, but keep getting stuck.
 
I appreciate your help in advance.