user: Question: what is the position for the United States U-20 affiliation 
Columns: ['Pick #', 'MLS team', 'Player', 'Position', 'Affiliation']
Types: ['real', 'text', 'text', 'text', 'text']
Sample row: [1.0, 'Vancouver Whitecaps FC', '* Omar Salgado', 'Forward', 'United States U-20']
SQL:

assistant: SELECT "Position" FROM "Table" WHERE "Affiliation" = 'United States U-20';