Kitchen broke a tie in the 70th minute, scoring on a header off a corner kick.
DeLeon opened the scoring in the 54th minute, and Luke Moore tied in the 60th.
Bradley had a good scoring chance in the 34th minute, but the U.S. midfielder's shot went wide.
"I felt good, excited to be back," Bradley said. "I'm disappointed that the game went the way it did, because this was a big game against a team close to us in the table and it would have been nice to capitalize."
United improved to 8-5-4, and Toronto dropped to 6-5-3.