Frenchman Muller said the country is special to him as he prepares to defend a 17-point lead over the final four race weekends of the season.
"It is certainly a big thing for the WTCC to be racing in the US for the first time, and everybody is excited," said Muller.
"This is especially the case for me as I’m a great fan of the US, and of the American culture and way of life.
"I have never been to Sonoma, so there is little I could say about the track. I will approach this round as always – trying to do the best I can on and off the track.
"We’re entering the final straight of the championship and things are starting to get serious."
Team-mate Rob Huff is closest to him in the championship, with third Chevrolet driver Alain Menu third another 20 points back.
Muller cannot wait for the competition to start up again after the two-month break and said he kept himself busy on two wheels rather than four.
"It’s nice to go back to racing after the summer break," he said. "In truth, I continued racing over the last few weeks, but on my bicycle.
"I prepared well for the Le Mans Biking 24 Hours at the end of August, but things did not go that well. We entered the challenge as a two-man team but unfortunately we pulled out after nearly nine hours of cycling after my team-mate suffered an injury.
"I could not finish the race alone.”
Muller won the title in 2008 with SEAT and 2010 and 2011 with Chevrolet.
The manufacturer announced recently that it will leave the WTCC at the end of the season despite dominating the series since 2010.