Error Code: 1136. Column count doesn't match value count at row 1
Change from 

SELECT
    @countryname
FROM
    (
    SELECT
        @countryname AS countryName,
        @nationality AS nationality,
        @countryprefix AS countryPrefix

to

SELECT
    @countryname AS countryName,
    @nationality AS nationality,
    @countryprefix AS countryPrefix