One of the most hotly contested series of the Pan American Games got under way today and the result was a resounding U.S. victory.

The sport was softball and only three of Cuba's nine batters were able to put their bats on the ball as Dave Scott struck out 15 in the six innings that were required for the U.S. to breeze to a 12-0 victory.

Two Cubans were out on infield grounders. Another, Daniel Dominguez, bunted and was ruled safe on a controversial call in the fifth inning for the only hit off Scott.

"I honestly thought he was out and it would have been nice to throw a no-hitter," said Scott, who walked two. "But it's no heartbreaker. The score was 8-0 USA at the time and that was the important thing. The way they were swinging, I don't think they've seen anybody throw that fast before."

The one-sided contest, halted an inning early because of the 10-run rule, came as a surprise to the U.S. team, which had been upset by Argentina Tuesday night.

"They'd been hitting real well, with 27 runs in two games," said U.S. Coach Rocco Santilli. "But after we lost last night, I think it lit a couple of fires here. Dave was the best I've seen him pitch. He had good velocity and a good drop."

While the Cubans were lunging at Scott's fast balls, trying to make some contact, the U.S. batters were totaling 15 hits, including home runs by Chuck Prescott, Mike Hazel, Mickey Brusco and Stu Dunlop.

At one point, with a new ball in the game, Scott stopped and pointed to the ball and his head.

"The new ball was very slippery and I tried to tell the umpires somebody might get hit in the head," Scott explained.

Accordingly, play was halted while a policeman, watching from the expressway beyond the outfield, slid down an embankment to retrieve the home-run balls.

For Cuban fans, if there were any present, there was literally nothing to cheer about.

When Eusebio Cruz fouled a ball beyond third base in the sixth, the only time the Cubans hit one past the infield, there were derisive cheers from Venezuelan spectators.

The two teams exchanged gifts before the game and shook hands afterward. There was a bit of a problem with the third-base umpire, a Bahamian, who twice called balls on batters because Scott had moved forward off the pitching rubber.

One call resulted in a walk when the batter had apparently struck out and Santilli yelled, "It goes both ways. Don't be a wise guy."

Three homers came off Gilberto Hernandez, second of three Cuban pitchers, and possibly the oldest participant in the Pan Am Games.

"He says he is 45, but that is not true," said Juan Fernandez, a Cuban reporter. "I am 51 and I know he's older. I think maybe he means 45 years pitching."

The players sat on benches behind a temporary fence while workmen continued to prepare the dugouts. Four days ago, there were no seats in the grandstand of the new park in this Caracas suburb, but they were in place for Monday's start of play.