Clark scored 98.00 for her eighth career World Cup win and third in a row while she also becomes the first US freestyle snowboarder to secure a ticket to the Olympics.
Reigning world champion Arielle Gold placed second behind the soon-to-be four-time Olympian with 91.25 with Gretchen Bleiler third in Copper Mountain with 86.00.
"I love the Olympics. I love the opportunity to get to go every four years. But for me, it really is about the tricks. It really is about my riding. It's about pushing myself," said Clark.
"So even though I had the contest wrapped up at the end there, it was still important for me to go out and put down a good run that I could walk away being really proud of.
"I was happy to put down a good first run and to come out and land the run that I wanted in my second run. I had a bit of a bug in the morning and I literally got off the couch at 5.30am for practice.
"People were bringing me soup and Gatorade all day. I was hurting and trying to conserve my energy in practice.
"That was the first 1080 I did all day, just because I was trying to make sure I had enough energy to put runs down when I needed to."
Meanwhile Taylor Gold, who just sneaked into the men's snowboard halfpipe World Cup final in Copper Mountain in 16th and last remaining place, took his first career win.
He posted 90.25 for an unexpected victory on his seventh World Cup start while USA teammate Gregory Bretz was second with 87.75 and Ben Ferguson third with 87.00.