I have taken a look and can see the problem. Your user's are not storing the country abbreviation, they are storing a numeric index value. You will need to use a join query to join the country table and the visitor table. I have made this update to your checkout page for you so that you can have a working example.
Along with making it a join query you will need to update the column that you are comparing to inside of the country select list. Currently you are comparing to:
Instead you will need to compare to the country name like this: