The Potomac Jets basketball team, representing the Washington, D.C., area, today learned the perils of being king of the hill. The top-seeded 15-and-under boys team in the AAU/USA Junior Olympics was almost upset by l7th-seeded Bloomington, Ind.

"It isn't going to be easy. Everybody's coming out after us," Kevin Parker, 14, said after the Jets' 72-70 victory. "That's what I like about it."

The Jets rallied from a seven-point deficit at the half.

"It took the whole first half for us to loosen up," Parker said. The freshman-to-be at Mackin High School explained that the Indiana team had played in the first round Wednesday night, defeating its home-state rival from Indianapolis, 76-56. The Washington team drew a bye.

Parker, the team's 6-foot-7 center, scored 23 points today, as did teammate Ernest Bruno, a 6-4 forward who attends Mackin.

"It was the fundamentals--don't get upset by a call, just play ball--that's what pulled us through," Bruno said.

Friday, the Jets face the team from Arkansas, which today defeated Independence, Mo., 71-68, after a first-round victory over Fresno, Calif. Arkansas has two players who reportedly average more than 30 points a game.

"But they score at least 15 to 20 points on fast breaks," Potomac Coach J.R. Watkins said. "We can keep them from doing that by using our guards so one of them is always in position to intercept."

The Jets won the AAU Junior Olymics tournament last year in Kansas City, Mo.

Twenty-eight teams are entered in the 1982 tournament at Memphis State University. Team members make up a large number of the more than 3,500 athletes who proved themselves good enough to represent at least 3 million youths who compete each year at local levels.