SELECT MIN(round) FROM table_name_19 WHERE nationality = "united states" AND college_junior_club_team__league_ = "breck school (ushs)"
Babak mana yang memiliki kewarganegaraan Amerika Serikat, dan tim perguruan tinggi/junior/klub (liga) Breck School (USHS)?
CREATE TABLE table_name_19 (round INTEGER, nationality VARCHAR, college_junior_club_team__league_ VARCHAR)