CREATE TABLE table_name_5 (opponents_in_the_final VARCHAR(255), score VARCHAR(255), championship VARCHAR(255), year VARCHAR(255))
which opponents in the u.s. championships played after 1945 and had a score of 3–6, 6–4, 2–6, 6–3, 20–18?
    
SQL: SELECT opponents_in_the_final FROM table_name_5 WHERE championship = "u.s. championships" AND year > 1945 AND score = "3–6, 6–4, 2–6, 6–3, 20–18"