CREATE TABLE table_204_521 (id NUMBER, "rank" NUMBER, "name" CLOB, "nationality" CLOB, "time  ( hand ) " CLOB, "notes" CLOB)

how many times did the united states rank ?
SELECT COUNT(*) FROM table_204_521 WHERE "nationality" = 'united states' AND NOT "rank" IS NULL
SELECT COUNT(*) FROM "table_204_521" WHERE "nationality" = 'united states' AND NOT "rank" IS NULL