1 carried on from the early work of underdog compatriot Jordan Thompson, who stunned Jack Sock in four sets to give the hosts a flying start at a packed Pat Rafter Arena.
Australia off to ideal Davis Cup start after Jordan Thompson's four-setter.
"I'm looking forward to getting back here and having some home support", said Kyrgios, who had to deal with a hostile crowd when he lost to Federer in Miami last week.
"I think we saw something special there", he said.
Saturday's doubles rubber could seal the deal for Australia, with John Peers and Sam Groth due to take on Sam Querrey and Steve Johnson.
Kyrgios looked confident and untroubled throughout his encounter with Isner.
Late in the first set of the doubles, former Australian Davis Cup victor Todd Woodbridge said on Channel Seven commentary that Sock looked as "flat as he was when he finished the match" on Friday.
Australian number one Nick Kyrgios plays John Isner in the second singles rubber later on Friday.
But teammate Jordan Thompson's 6-3, 3-6, 7-6 (7-4), 6-4 win over American Jack Sock, the highest-ranked player in the tie at No.15, set the Americans back on their heels.More news: Kyle Lowry returns, Raptors beat Pistons 105-102
The winners of the tie will face either Serbia or Spain in the semi-finals.
"Thommo in only his second live Davis Cup match, that was pretty impressive", he said.
"And whatever we think collectively is going to help us have the best chances is what everyone signed up for".
The oft-controversial wunderkind Kyrgios got the better of Isner, winning in straight sets, when they last faced each other at the Atlanta Open in 2016; but Isner has the advantage in the head to head, beating the firebrand Australian, ranked 16th in the world, in their two other matchups to date.
"I've been playing great tennis".
"I definitely feel like I've really put in an effort to try and do it consistently".
But the USA soon clicked, firing back to win the second and third sets as Sock rediscovered his touch and his confidence.
The Australians were clearly feeling the energy from the singles rubbers on day one, with Groth and Peers bounding out of the blocks as they tried to steal a march on the American duo.
American captain Jim Courier said on Friday night that the United States team would "rally" around Sock, a former Wimbledon doubles champion, after he had finished with energy tanks near empty in a four-set loss to the lower-ranked Jordan Thompson.