Matrix custom Column Total

I would like to incorporate the visual below into a Matrix. This visual shows taxes paid by different groups. Within the matrix I would like to place location in the column section of the matrix. The matrix columns would show “World”, “U.S” and “International”. The challenge is, “World" is not an actual column in my data set. The world column is just the combination of the U.S and International columns added together. Is there a way to create measure that allows me to add a "World" column to the matrix at the same hierarchical level as U.S and international?