He was released on bond and is due to appear in court on May 27.
Fonda covers a wide range of topics in "My Life So Far," including her 1972 visit to Hanoi to protest the Vietnam War, during which she was photographed on a North Vietnamese anti-aircraft gun. She has apologized for the photo, but not for opposing the war.
Smith, a Vietnam veteran, told The Kansas City Star Wednesday that Fonda was a "traitor" and that her protests against the Vietnam War were unforgivable. He said he doesn't chew tobacco but did so Tuesday solely to spit juice on the actress.
"I consider it a debt of honor," he told The Star for a story on its Web site. "She spit in our faces for 37 years. It was absolutely worth it. There are a lot of veterans who would love to do what I did."
Fonda, who flew to Minneapolis Wednesday for another appearance on her book tour, issued a statement through Jynne Martin of Random House.
"In spite of the incident, my experience in Kansas City was wonderful and I thank all the warm and supportive people, including so many veterans, who came to welcome me last night," she said.
Fonda drew a crowd of about 900 at Unity Temple, said Vivian Jennings, whose Rainy Day Books of suburban Fairway, Kan., sponsored the event.
Jennings said the 67-year-old actress never got up from her seat and continued autographing books after the tobacco juice was wiped off.
"The important thing is that she was so calm and so gracious about it," Jennings said. "She was wonderful."