Here's an example of a World map linked to a US map (click on the United States):
Download the above demo and reference the source code as I explain how the above example was created.
Customize your US map and World Map independently.
Rename the US mapdata.js file to mapdata_us.js so that it doesn't conflict with the World mapdata.js file.
In the mapdata_us.js file set auto_load: 'no',. This will keep the US map from loading until it is clicked.
In the mapdata_us.js file set
This will make the back button will appear after the US has been clicked. Clicking on this button will take the user back to the world map.
That's it. Your two maps should now be linked!