Who is the tallest player in team USA U20?
tallest refers to MAX(height_in_cm); 
player refers to PlayerName; team USA U20 refers to TEAM = 'USA U20';
SELECT T.PlayerName FROM ( SELECT T1.PlayerName, T3.height_in_cm FROM PlayerInfo AS T1 INNER JOIN SeasonStatus AS T2 ON T1.ELITEID = T2.ELITEID INNER JOIN height_info AS T3 ON T1.height = T3.height_id WHERE T2.TEAM = 'USA U20' ORDER BY T3.height_in_cm DESC ) AS T WHERE T.height_in_cm = ( SELECT MAX(T3.height_in_cm) FROM PlayerInfo AS T1 INNER JOIN SeasonStatus AS T2 ON T1.ELITEID = T2.ELITEID INNER JOIN height_info AS T3 ON T1.height = T3.height_id WHERE T2.TEAM = 'USA U20' )