De Kock leads South Africa to 194-4 against USA at T20 World Cup
Opening batsman De Kock, his country's leading run-maker in the format, reached his 15th T20 international fifty off 26 balls in the opening game of the Super Eights stage at the Sir Vivian Richards Stadium.
He was eventually dismissed for 74 with seven fours and five sixes in a 40-ball innings which was comfortably his best performance of the tournament.
In four previous visits to the crease at the World Cup, the 31-year-old had a best of just 20 against Sri Lanka.
Skipper Aiden Markram also hit his tournament best of 46 from 32 balls with four boundaries and a six.
Markram and De Kock put on 110 for the second wicket and helped their team reach 101-1 off the first 10 overs.
Slow left-armer Harmeet Singh brought the United States back into the match by removing De Kock and fellow dangerman David Miller (0) in the space of two balls.
Markram's innings was ended by impressive fast bowler Saurabh Netravalkar who finished with 2-21 from his four overs.
Heinrich Klaasen (36 not out) and Tristan Stubbs (20 not out) added an undefeated 53 for the fifth wicket.
USA qualified for the Super Eights by finishing second behind India in Group A after notching a famous win over Pakistan in Dallas.
South Africa, who topped Group D with four wins from four, made one change from their last outing against Nepal with spinner Keshav Maharaj coming in for medium-pacer Ottniel Baartman.
West Indies and defending champions England are the other teams in Group 2 of the Super Eights.
India, Australia, Afghanistan and Bangladesh comprise Group 1.