The former Everton star struggled to make an impact as his teammates failed to match the Dynamo's energy.
"That was tough. They were putting a lot of balls into the box, set plays, and even open play; it just wasn't our night tonight. I think a few boys come off injured, the team changed a few times, and it planned that I'd play for 90 minutes, but in those games, you just play.
"I've got to get as much fitness out of them. I definitely felt it; it was tough. It was a different sort of heat and everything. I don't like to make excuses. I just play football and they are good team. They had some nice stuff. They disoriented the team a little bit and we struggled and conceded two goals," Cahill told the New York Post.
"I've played throughout the season in Qatar and places like Australia. I think that this was still quite a good tempo, especially in this heat. It's different. I trained once with this team and then play the whole 90 minutes; it's pretty full on. I think that this is what is going to be expected with MLS."