The tournament favourites will face Mexico in the last-16 in Barcelona on Saturday, after winning all five matches in Group C in Bilbao by an average of over 33 points.
After downing Ukraine 95-71 on Thursday, Krzyzewski said he was pleased with their output - and also waved away fears of an injury to point guard Kyrie Irving.
"5-0 and healthy. We are happy going forward," he said.
"Kyrie is fine. He took a blow on his tail-bone, but I think he'll be fine.
"I think it's tough on all the teams to play five games in six days. Overall I think we have played well. We have shared the ball well. I think we have worked very hard defensively."
Krzyzewski said the one criticism he had of their start to the tournament in Spain were attacking deficiencies.
"Our offense was not all that good for the first quarter tonight (USA trailed 19-14) and for the first half against Turkey (USA trailed 40-35), but defensively we have been excellent all along," he said.
On their upcoming opponents, Krzyzewski said Mexico had some youthful talent.
"We still haven't studied them," Krzyzewski said.
"We know they have a couple of good young players, but we haven't studied their strategies yet."
Mexico forward Marco Ramos said the Central Americans' progression to the last 16 - their first trip to the knockout stages in their history - was momentous.
After 40 years out of the World Cup, Mexico's return to the competition got even better when their second win of the event - an 87-71 win over South Korea - took them into a showdown clash with the Americans.
"Today was a very important day for the history of Mexican basketball," he said.
"We are very proud, we're a very proud country, a very proud team, we have a great coach and great coaching staff, and today we made history."