It wasn't Miss USA's night.

Booed mercilessly at the Miss Universe pageant by a Mexican audience angry at U.S. immigration policy, and seen by millions of TV viewers as she slipped and fell on the pageant stage, Miss USA Rachel Smith nonetheless managed to take the high road and offer her Spanish-speaking hosts an enthusiastic, "Buenas noches Mexico. Muchas gracias!"

Smith, 22, from Clarksville, Tenn., who was crowned Miss USA last March, was continuously jeered by the mostly Mexican audience during the pageant's interview phase.

The pageant was won by Miss Japan, Riyo Mori, a 20-year-old dancer, marking only the second time her country has won the world beauty title.

Miss USA finished fifth.

Pageant owner Donald Trump downplayed the booing, saying it was aimed at American policies and not Smith.

"We believe it wasn't Rachel being booed but the USA and some of our policies as a country," pageant spokeswoman Lark-Marie Anton told FOXNews.com. "The booing was unfortunate, but Rachel represented the USA with style and grace. She was extremely dignified.

Asked whether the Mexican audience reaction would affect the pageant's return there, Anton said: "The Universe pageant traditionally goes to different countries yearly, so we wouldn't have the pageant in Mexico next year. Mr. Trump also mentioned in last night's press conference the possibility of Japan as a host country for next year."

She added that it would be "drastic" to never have the show in Mexico again because of Monday night's crowd reaction.

Mori, meanwhile, suffered her own minor slip when she found out she'd won the pageant.

Nervously grabbing the hands of first runner-up, Natalia Guimaraes of Brazil, just before the winner was announced, she threw her hands up and covered her mouth, tipping the $250,000 diamond-and-pearl-studded headpiece from her head. She quickly caught it and placed it back on her head.

• PHOTO ESSAY: The Miss Universe 2007 Competition

The last time Japan won the pageant was in 1959 when Akiko Kojima became the first Miss Universe from Asia.

Mori, from the small town of Shizuoka at the base of Mount Fuji, won the cheers of the Mexico City audience when she opened her interview, saying 'Hola, Mexico!'

"I learned how to always be happy, be patient and to be positive, and this is what I want to teach to the next generation," she said during the interview competition.

The daughter of a dance school operator, Mori said her grandmother told her as a child that she wanted her to be Miss Japan before she turned 20.

"From the very beginning, I entered the competition with high hopes and an unswerving determination to make this dream a reality," she said in a pre-competition interview.

She wants to someday open an international dance school in Tokyo.

"Right now I am only 20 years old, so I'm really excited about what I'm going to be able to do at this age to benefit society," Mori said after winning.

Also finishing in the top five were second runner-up Ly Jonaitis of Venezuela and third runner-up Honey Lee of Korea.

The winner travels the world for a year on behalf of charities and pageant sponsors.

Missing from this year's contest was Miss Sweden, whose country is one of the few to win the crown three times. Isabel Lestapier Winqvist, 20, dropped out because many Swedes say the competition does not represent the modern woman.

Hours before the pageant began, dozens of protesters held a mock ceremony in downtown Mexico City that featured "Miss Marijuana," "Miss Sexual Health," "Miss Human Rights" and other candidates with obscenities written across their sashes. The group yelled "Neither ugly nor beautiful, should a woman be considered an object!"

Pageant organizers say the Miss Universe contest carefully selects women who are intelligent, well-mannered and cultured.

The pageant was last held in Mexico City in 1993, when Torres was crowned.