"Now you know why I'm not managing anymore,'' Leyland said with a laugh.
He and his players could smile only afterAdam Joneshit the winning RBI single with two out in the 10th to beat Colombia 3-2.
The Americans improved their all-time WBC record to 11-10. They failed to make the finals in the three previous events and next face the Dominican Republic, the defending champion.
"I'm hoping this win takes a little bit of pressure off and we can relax a little bit,'' Leyland said. "You don't relax against the Dominican Republic, but at least the guys feel good they got a win under their belt.''
U.S. starter Chris Archer retired all 12 batters he faced. Archer, coming off a 9-19 season with Tampa Bay, struck out three and needed only 41 pitches to get through four innings.
He left the game well shy of the limit of 65 pitches for the first round because the Rays had requested that Archer pitch only four innings, Leyland said.
"It was tough, but we stuck to the plan,'' Archer said.
Colombian starterJose Quintanawas also dominant, holding the Americans hitless until Brandon Crawford singled with two out in the sixth. Quintana was then pulled because he had thrown 63 pitches, and Colombia's 2-0 lead was soon gone, too.
William Cuevas gave up an RBI double to Jones and threw a wild pitch that allowed the tying run to score in the sixth.
With one out in the 10th, Christian Yelich and Crawford walked against Guillermo Moscoso, and both advanced on a groundout. The noisy crowd of 22,580 was on its feet when Jones lined a single on an 0-2 pitch and was mobbed by his teammates.
Pat Neshek struck out Jesus Valdez with two on to end the Colombian ninth. Tyler Clippard pitched around a walk in the 10th to earn the win.
The Americans won with only six hits.
"At times we were probably trying to do too much,'' Leyland said. "We were probably a little anxious.''
Marcus Stroman is scheduled to start for the United States against the Dominican Republic's Edinson Volquez before a sellout crowd Saturday night. The Dominicans won their opening game Thursday against Canada.
The Colombians were making their WBC debut after qualifying for the first time, and they took a 2-0 lead with three consecutive two-out doubles in the fifth off Mychal Givens. Valdez pulled a ball into the gap to become the Colombians' first baserunner, and Adrian Sanchez and Mauricio Ramos followed with RBI hits.
Single-A center fielder Tito Polo of Colombia retreated to make running catches and rob Jones and Ian Kinsler of extra-base hits, and made a sprawling catch of Nolan Arenado's liner with the score tied and two on to end the eighth.
The Colombians had a chance to break a 2-all tie with two on and one out in the eighth, but Gold Glove third baseman Arenado turned an inning-ending double play.
"The end was not good,'' manager Luis Urueta said, "but this shows what Colombian baseball is.''
PUERTO RICO THUMPS VENEZUELA, 11-0
Carlos Correa, Yadier Molina and T.J. Rivera homered, and Puerto Rico beat Venezuela 11-0 in seven innings Friday night in Group D of the World Baseball Classic.
Correa connected for a solo shot and Molina added a two-run drive in the sixth inning. Rivera belted another two-run homer in Puerto's Rico's six-run seventh, finishing the game. In the World Baseball Classic, a team gets the win with a difference of 10 or more runs after five innings.
Seth Lugo, Giovanni Soto and Joe Jimenez combined on a three-hitter. Lugo, a right-hander for the New York Mets, struck out three in 5 1/3 innings.
"Seth was the key, he was very efficient and he took us to the fifth inning and that gave us a chance to be more aggressive with the bullpen,'' Puerto Rico manager Edwin Rodriguez said. "But we also have Correa who did everything, he stole bases, was very good at third base, he also hit a home run and gave us quality at-bats, we knew that we had the kind of team where someone is going to step up, we had a very good team effort tonight.''
Miguel Cabrera, Odubel Herrera and Ender Inciarte had the only hits for Venezuela. Seattle Mariners right-hander Felix Hernandezgave up two runs, one earned, in 2 2/3 innings.
"I have never lost like this, but we need to stay upbeat for the next game,'' Cabrera said.
Puerto Rico takes on Mexico in its second WBC game on Saturday. Venezuela will play against Italy.