CoCo Vandeweghe beat France's Caroline Garcia 6-4, 6-2 to reach her first career clay court final at the Stuttgart Grand Prix on Saturday and admitted she was winning matches by not taking things too seriously.
The last American to reach a final in Germany's automotive capital was Lindsay Davenport in 2005.
On Sunday, Vandeweghe will face either fifth seeded Czech Karolina Pliskova or Anett Kontaveit of Estonia who meet in Saturday's other semi-final.
The 16th ranked Vandeweghe has proved a revelation this week on a surface that she has never shone on before, seeing off world number one Simona Halep in the quarter-finals.
"I'm playing relaxed, chill," the 26-year-old, with a pair of Dutch grass court titles on her WTA curriculum vitae, said.
"It's like I'm on the beach in California. I wouldn't say that I don't care, but I'm not taking the matches deadly seriously.
"I'm one step closer to the title (and a flame-red Porsche 718 Boxster which has been on display by the court all week). I'm excited to be in the final."
Vandeweghe loosened up a tight first set in the ninth game with a break of her French opponent who was a semi-finalist at the tournament last year.
The Californian earned a set point a game later as she chased a drop shot and produced a volley winner at the net.
Vandeweghe claimed the opener on the next point as Garcia drilled a forehand return wide.
The second set went quickly, with Vandeweghe breaking Garcia twice, taking command at 5-2 from a love break of the French player.
The unseeded America wrapped up victory in the next game with a service winner on match point after 74 minutes.
"I had to strike first," Vandeweghe said. "I needed to make her uncomfortable if I was to have a chance."
She leads her series with Garcia 2-1 and her final appearance on Sunday should move her to 14th in the rankings.
The American said that she has turned her mental attitude around over the past month, since losing her opening match in Miami, thanks to reflection during a week in the Bahamas.
"I needed to re-evaluate where the first part of the season had gone. I then went home to California and spoke to (coach) Pat (Cash) on the phone.
"I had to get over just the general unhappiness after Miami," said the player who beat US Open winner Sloane Stephens and defending champion Laura Siegemund in addition to Halep this week.
Vandeweghe thrilled locals by revealing that her maternal grandmother once lived in the nearby town of Pforzheim, 50 kilometres north-west of Stuttgart, giving her a German connection.
CoCo Vandeweghe serves up defeat for Caroline Garcia to book first ever clay court final appearance