Incomplete number of rows in filtering by ORDER OF EXPRESSION

I am having difficulties with the code below
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My Code:

SELECT customer_id, first_name, last_name, country,
   WHEN country ="Canada" THEN "Canada"
    WHEN country ="USA" THEN "USA"
 END AS new_country
 FROM customer
 ORDER BY country desc

What do you get with your answer? Can you tell why it doesn’t satisfy the instructions?