The Leeds United forward was called up into the Scottish squad on Wednesday night to replace injured former Huddersfield Town front man Jordan Rhodes.
The Blackburn player was forced to withdraw after rolling his ankle during a training session.
McCormack, who has scored six goals in two games for Leeds, was initially omitted when Strachan picked his squad to face the USA at Hampden Park tonight.
“Ross is excited to get back in the squad,” said Strachan. “I spoke to his manager and they are very pleased with him.
“He had a wee change of positional play at Leeds which (manager) Brian (McDermott) thinks has helped him to score more goals and we will take that on board.”
McCormack scored all four goals for Leeds in their 4-2 win at Charlton last weekend, a week after grabbing a brace against Yeovil.
On Rhodes, Scotland’s manager commented: “Jordan had to go back. He was unfortunate to go over on his ankle when there was no one near him.
“He has had two strange injuries when he has been here. He has broken his hand and this time he went over on his ankle. That is a pity.”
Strachan is looking forward to meeting up with USA coach Jurgen Klinsmann, against who he played when he was at Coventry and the former Germany striker was at Tottenham.
“He is a terrific footballer, a terrific man and a great character,” said former Leeds captain Strachan. “He has brought a lot to the game with his enthusiasm and he can laugh at himself at times as well.
“He was a great ambassador for German football when he was in England; he has been a great ambassador for German football everywhere he goes.”
Ther USA are using the game as preparation for the 2014 World Cup finals in Brazil next summer and will also play against Austria in Vienna next week.