Gomez, 29, left the pitch inside the opening 10 minutes of the match in Nashville, with goals from Kieran Morrison, Dominik Szoboszlai, Federico Chiesa and Lewis Koumas then earning Liverpool the win.
"A lot of things to correct, obviously, it's the first day. You could feel the heavy legs, the players have been training," Iraola said in an interview on the club's website.
"So, we lacked some freshness. But it will give us a good starting point to improve things. Probably the worst news has been straight away the injury of Joe.
"We were happy because we were kind of going through all the training without losing any player. Unluckily for us, straight away we've lost Joe."
The Spaniard added that centre-back Jeremy Jacquet, whose previous season was cut short by a shoulder injury before his summer move to Liverpool, is likely to feature in their pre-season preparations.
"He has been a lot of months without playing with a shoulder injury. So, I think we are going to take it easy with him," he added.
"He will play probably the last game of this US tour and he will have time to have minutes."
Liverpool play pre-season games against Wrexham, Leeds United, AS Monaco and Como, before their first match of the Premier League season away to Newcastle on August 23rd.