The Dance Theatre of Harlem came on like gang busters at the Kennedy Center Opera House last night, opening its two-week run in the "Dance America" series with a razzle-dazzle, all-American program based on musical scores by Sousa, Bernstein and Gershwin.

Surely the company has never looked better, and quite possibly never so good. Artistic director Arthur Mitchell recently resumed teaching company classes, and he told us we'd see the difference. We do. More than ever, the troupe seems molded in the image of Mitchell himself in his earlier, performing years with the New York City Ballet. The DTH dancers have fastened onto the qualities of mercurial sparkle and zest that made Mitchell unique as a dancer, but they've reinterpreted these attributes in terms of their own youthful generation. The result is a company that seems more assured, more vibrant and more distinctly itself than at any previous time in its 15-year history.

Fittingly enough, just as President Reagan was delivering his State of the Union address, DTH was blazing through George Balanchine's "Stars and Stripes," set to marches by John Philip Sousa as arranged by Hershy Kay. Once asked if this patently abstract ballet had a story, Balanchine replied, "Yes . . . the United States." Indeed, this incredible halftime pageant in toe shoes is living proof that a naturalized, patriotic citizen could give his Russian classical tradition an unmistakably American accent.

The DTH performance pulled out all the stops. Especially memorable were charming, slender, high-stepping Charmaine Hunter leading the first "regiment"; the sharply honed virtuosity of Joseph Cipolla, along with his gutsy ensemble of men, ending the third "Campaign" with double air turns in unison; and the whirlwind pyrotechnics of Judy Tyrus and Eddie J. Shellman in the penultimate duet. The stage-filling finale, with its Old Glory backdrop, summed up the corny but thrillingly rousing spirit -- really quite Reaganesque -- of the whole ballet.

"Stars and Stripes" is a closing ballet if ever there was one, and it was hard to imagine how the troupe could surpass itself after this. It did, nevertheless, with its wonderfully swinging, piquant performance of Jerome Robbins' "Fancy Free," acquired for the repertory, like "Stars," just last year. It may seem odd to speak of bringing refreshment to a ballet that's never lost its freshness in countless performances by American Ballet Theatre and the New York City Ballet since its premiere in 1944. But DTH hasn't duplicated any past versions -- it has taken possession of the ballet and given it a bright new face. It's hard to recall the story of the piece -- about three sailors on shore leave, trying to pick up girls -- being quite so lucidly set forth, or the characterizations more winningly accomplished. The dancing, too, has a new, flinty clarity to it, even in tiny details like the tap riffs the sailors casually let fly. Conductor Milton Rosenstock's account of the zippy Bernstein score also adds unaccustomed burnish. And the cast principals were knockouts, one and all -- Donald Williams, Cubie Burke and Tyrone Brooks as the gobs, and Hunter, Christina Johnson and Theara Ward as the gals.

The company wound up with its premiere of "Concerto in F" to the familiar Gershwin score, restaged en pointe for DTH by choreographer Billy Wilson, who originally mounted the piece on Alvin Ailey's modern dance company in 1981 but envisioned it from the start in toe shoes. It's a splendidly frothy, well-crafted ballet that smoothly fuses classical and jazz dance vocabularies. The point work, smartly extending the female leg line, seems entirely congenial to Wilson's style and it also helps accentuate the company's sexy attack.

If there was a problem with the program, however, it was the too close kinship of "Concerto" and "Fancy Free," manifest even in the nocturnal skylines of the two sets, and pinpointed in Wilson's middle movement, a blues playlet for three dancers that parallels the Robbins in its basic premise -- one male too many. None of this, however, dampened the company's scintillating performance, with a cast headed by the extraordinary Stephanie Dabney (of "Firebird" fame) partnered by Williams in the first movement, and Hunter, Cipolla and Hugues Magen as the skirmishing threesome of the second. David LaMarche was the lively, adept piano soloist, under Rosenstock's direction.

There's a lot more to come in the DTH engagement, which includes four more programs spanning 11 ballets by 11 different choreographers. If the starter is any indication, it's going to be a whale of a series.