Ten of Scotland's starting line-up had fewer than 10 caps, with seven making their first international start, and they found the going tough against an inspired USA side who registered their first win over Tier One opposition.
"It was a tough one. All credit to America, they took their opportunities when they were there," Hogg said.
Scotland made the best possible start when Hogg put Blair Kinghorn in for the game's opening try within 60 seconds. A penalty try and a George Turner touchdown - the hooker's fourth in two matches - looked to have set the tourists on course for victory.
The boot of fly-half AJ MacGinty kept the USA within touching distance, and the tide began to turn when Joe Taufete'e scored late in the half for the home side.
Taufete'e touched down again shortly after the break, and when MacGinty pounced on a Matt Fagerson error to put Hanco Germishuys in for a try, the Scots were in trouble at 30-24 down.
Head coach Gregor Townsend made a raft of substitutions in an attempt to rescue the game, and Dougie Fife came off the bench to score two minutes beyond the 80. That allowed Kinghorn a conversion to snatch victory, but his touchline kick sailed wide of the target.
"For us we've got to learn, and learn quick," said Hogg, who captained Scotland for the first time in Houston.
"We weren't good enough from the get-go. We scored a nice try early on and after that shut off and went to sleep."
Scotland now head for Argentina to face the Pumas in their final summer tour match.
"Like I say we've got a lot to learn and we've got to do it quick because we've got another tough test next Saturday," Hogg added.