Five of the six U.S. women wrestlers are undefeated after the first day of competition at the 2001 Pan American Women's Wrestling Championships, in Santa Domingo, Dominican Republic, May 17-20.    Held three of every four years during the non-Pan American Games years, the Pan American Championships features the best wrestlers in North, Central and South America.     Among the unbeaten Americans is 2000 World champion Kristie Marano (Albany, N.Y./ATWA) at 149.75 pounds.Marano pinned Sumergida Tejada of the Dominican Republic in the first match, then defeated veteran Xiomera Guevara of Venezuela, 7-1 in the second match.    Four 2001 U.S. Nationals champions also went unbeaten during the first day for the United States: Stephanie Murata (Lansing, Mich./Sunkist Kids) at 112.25 pounds, Tina George (Colorado Springs, Colo./Sunkist Kids) at 123.25 pounds, Sara McMann (Lock Haven, Pa./Sunkist Kids) at 136.5 pounds and Iris Smith (Colorado Springs, Colo./Sunkist Kids) at 165.25 pounds.    Murata scored a pin over Ivelisse Nunez of the Dominican Republic in the first round, then stopped Magdelena Arellano of Mexico, 11-3 in the second match.    George dominated her opponents, winning by technical fall over Vesmeica Santos of Dominican Republic, 11-1 and pinning Angela Peraza of Venezuela in just 22 seconds.    McMann had just one match during the day, pinning Lil Azucena of El Salvador.    Smith defeated Yamilezt Ramos of Venezuela, 9-1, to open the tournament, then pinned Arelis Taveras of the Dominican Republic in 40 seconds in the next round.    2000 U.S. World Team member Clarissa Chun (Kapolei, Hawaii/Missouri Valley) had a 1-1 record at 101.25 pounds. Chun opened with an 11-1 technical fall over Ingrid Cuellar of El Salvador, then dropped a 10-4 decision to Mayerly Caripa of Venezuela.    The competition will be completed on Friday, May 18. The United States is the defending Pan American Championships team champion in women's wrestling. Smith was one of three U.S. champions at the 2000 Pan American Championships, which were held in Cali, Colombia.     PAN AMERICAN WOMEN'S WRESTLING CHAMPIONSHIPS  at Santa Domingo, Dominican Republic, May 17  U.S. Women's freestyle team results    46 kg/101.25 lbs. - Clarissa Chun, Kapolei, Hawaii (Missouri Valley) - won by tech. fall over Ingrid Cuellar (El Salvador), 11-1; lost dec. to Mayerly Caripa (Venezuela), 10-4    51 kg/112.25 lbs. - Stephanie Murata, Lansing, Mich. (Sunkist Kids) - pin Ivelisse Nunez (Dominican Republic); dec. Magdelena Arellano (Mexico), 11-3    56 kg /123.25 lbs.- Tina George, Colorado Springs, Colo. (Sunkist Kids) - won by tech. fall over Vesmeica Santos (Dominican Republic), 11-1; pin Angela Peraza (Venezuela), 0:22    62 kg /136.5 lbs. - Sara McMann, Lock Haven, Pa. (Sunkist Kids) - pin Lil Azucena (El Salvador); bye    68 kg/149.75 lbs. - Kristie Marano, Albany, N.Y. (ATWA) - pin Sumergida Tejada (Dominican Rep.); dec. Xiomera Guevara (Venezuela), 7-1    76 kg/165.25 lbs. - Iris Smith, Colorado Springs, Colo. (Sunkist Kids) - dec. Yamilezt Ramos (Venezuela), 9-1; pin Arelis Taveras (Dominican Republic), 0:40    Coaches - Rob Eiter, Evanston, Ill.; Mike Duroe, Colorado Springs, Colo.