Which Round has a Nationality of united states, and a Player of jimmy hayes?
CREATE TABLE "draft_picks" (
  "round" real,
  "pick" text,
  "player" text,
  "position" text,
  "nationality" text,
  "club_team" text
);
SELECT MAX("round") FROM "draft_picks" WHERE "nationality"='united states' AND "player"='jimmy hayes';