CREATE TABLE table_204_521 (id DECIMAL, "rank" DECIMAL, "name" TEXT, "nationality" TEXT, "time  ( hand ) " TEXT, "notes" TEXT)

which competitor from united states had the longest time ?
SELECT "name" FROM table_204_521 WHERE "nationality" = 'united states' ORDER BY "time (hand)" DESC LIMIT 1
SELECT "name" FROM "table_204_521" WHERE "nationality" = 'united states' ORDER BY "time (hand)" DESC NULLS LAST LIMIT 1