I just did the attached for someone else, but it maybe useful for you
I just quickly added in some fake world regions, alongside real city, long/lat data
Using the world region on the colour tab works fine (assuming its not junk data like mine!)
I don't think Tableau can automatically map the 'world regions', so the best i think, is using on the colour tab to help differentiate.
FYI - the below is where all map information is stored for Tableau (it will depend what version your using)
C:\Program Files\Tableau\Tableau 8.3\Local\Data
CM_MF.twbx 178.1 KB
Out of date reply but to do this kind of stuff you can merge countries into custom regions and then easily import that into Tableau as an object so you don't have to modify your data to fit the visualization. It should be the other way around.
Simply take a world by country file and the data you have already organized in Tableau that maps your region to country.. Then import that into Region generator and it will spit out a Tableau formatted CSV file ready to be imported back into Tableau.
Full instructions are here: CMaps Analytics Region Creator