Good thing is your formula is correct, no problems there.
Anaplan is extremely logical so when something doesn't work, it usually guides you where to go. In this case since code isn't showing up and your formula is correct, you can be sure that code is not present in the Country Flat list.
The csv to be imported has three columns, make sure when you are importing into the list, you are mapping name to Country Name and code to Country code. I can see you have mapped Country code to name in the list (This would've happened since you did not change the import mapping and went with the default).
Note that you'd need to delete all items from Country Flat list first and then re-import to ensure you get the data right.