Please calculate negative critical reception of American movies
'negative critical reception' refers to percentage of movies with a rating of 1, which = [count(rating = 1) / count(all movies)] * 100% 
SELECT CAST(SUM(IIF(T1.rating = 1, 1, 0)) AS REAL) * 100 / COUNT(T1.movieid) FROM u2base AS T1 INNER JOIN movies AS T2 ON T1.movieid = T2.movieid WHERE T2.country = 'USA'