"I tried to be focused all the time, play aggressive".
Victory on Friday over Spain's Pablo Carreno Busta, another man in unknown territory in a maiden semi-final at a Slam, will make Anderson the first South African in a final at the majors in nearly 35 years.
After an early exchange of second-set breaks, Carreno Busta broke to 5-4 and held to claim the set, then broke at love on a double fault to open the third set.
Querrey appeared in control of the tie-break at 5-2 ahead, only for Anderson to reel off five consecutive points - the American sending a backhand return long on set point.
"But I feel like that's where I was able to really reset". "I had my opportunities and I did not capitalise on them".
Seven-time Grand Slam champion Venus Williams, this year's Australian Open and Wimbledon runner-up, faces two-time Wimbledon champion Petra Kvitova later for a berth in Thursday's women's semi-finals.
Next up in the last four is another tough match against Argentinian Spanish 12th seed, Pablo Carreño Busta.
Not since Wayne Ferreira at the 2003 Australian Open has a South African made the last four at a Slam, while Cliff Drysdale in 1965 was the last man to do so in NY, when the tournament was still amateur. "I really thought I did a fantastic job resetting".
It was a closer match than the scoreline suggested but, as in his fourth-round victory over Denis Shapovalov, Carreno Busta played the big points superbly.
Anderson has also capitalized on a draw which is missing 2012 victor Murray, two-time champion Novak Djokokic and the 2016 champion Stan Wawrinka, all absent through injury.
"We have become accustomed over a decade to seeing the same guys being there and they had such unbelievable consistency", he said.
"This is incredible at this stage", Anderson said in an on-court interview by ESPN.
"So obviously it gives us a bit of a chance to go deep into the tournament". "Only one guy can go through, and Kevin's pretty tough".
South African Kevin Anderson battled his way past American Sam Querrey as Tuesday night turned to Wednesday morning in Queens. "A lot of his balls were landing in". It's just tough. Just a couple points here and there.