If you know which countries belong to each region you could group them manually. Basically you are creating a group for each Region you want those countries to belong to (NA, APAC, EMEA).
Right click on your Countries field on the Data Pane and select Create then Group. Name you with a recognizable name , now you can scroll down the countries selecting the ones that belong to a specific Region. Once you have selected all the countries for one region you can rename that group with that Region's name. Do the same for the est of the countries. Your group field will appear then in your Data pane and then you can use it in your visualization.
hope this is helpful.