You could create a segmentation in the Lead Database section for the different regions, and then add waitsteps in the flow with "add choice" defining the different segments for sending the email by region.
Example Flow:
In my example, I used my currency tiers segmentation, but you would use "Region" or whatever you choose to name your Segmentation. This is the easiest way I can think to do what you are asking. If someone has a faster way, I'd love to hear it too!