Regional Uptime Chart

Make sure you have a custom property that tags which nodes belong in each region.  I'll call mine "Region" for example's sake.

Add a custom chart widget to a view, probably want to filter it to nodes where region is not blank.

On the section where it wants to know what stats you need to track find the node availability %

In the lower section where it says group by and legend shows just set them both to use your Region custom property.

Done.

I do the same approach as Mesverrum.. I have custom properties for Region, Country, and City to help organize my roughly 365+ locations. Then you can use those properties to generate all sorts of views and reports, etc..