With only a dozen territories to choose from, putting them directly int the pop-up menu seems a reasonable choice. Having done so, you could make the state appear automatically, using a LOOKUP table, with the territory names as the search key. Here's an example:
Column A on Main contains a series of pop-up menu cells, all with the same menu items.
Column A on Data contains the same items (Territory 'names') as the menus. Order doesn't matter, but 'spelling' must be an exact match.
There is a single formula on Main, entered in B2 and filled down and right from there. Nmbers automatically edits the formula to fit its new location. Manual editing is required in D2 before filling down, as I wanted values from column H of Data here, not from column D.
B2: =LOOKUP($A,Data :: $A,Data :: B)
Fill right to D2. Edit D2 to read: =LOOKUP($A,Data :: $A,Data :: H)
Select the three formulas and fill down to row 10.
Choose a territory in column A, and the information for that territory will fill in the rest of the row.