The Texan outfit took the lead in just the 11th minute when Scott Caldwell turned the ball into his own net.
However, Diego Fagundez was following up to restore parity with just over half an hour left to play.
The turnaround was complete seven minutes before the end when Nguyen won another penalty, this time from Lewis Neal. He made no mistake second time round, smashing straight down the middle to earn his side all three points.
Jay Heaps's men are in fifth place in the table, just a point ahead of Chicago Fire.