The opening here yesterday of Spoleto Festival, U.S.A., marks the first attempt to transplant a major international arts festival to this country.

The resulting glare of the national spotlight, though, appears to have taken this gracious, placid little Southern city quite by surprise, and left it blinking in bewilderment. The sudden jump from quiet proincialism to cosmopolitan celebrity seems, for the moment, more of a jolt than anyone here quite knows how to assimilate.

To some of Charleston's ordinary citizens nothing very much has changed. The woman cab driver, stolid and fiftyish, told me, "I don't think anyone is too excited about this thing. But I hear this fella on the TV - the guy that's leadin' the music part - say that the further on it goes, the more people they'll get."

The "guy" she meant was composer impressario Gian Carlo Menotti, Spoleto's founder-director. Minotti opened the first Festival of Two Worlds in Spoleto, Italy, 20 years ago.

At the opening ceremonies at the Cistern, an open-air courtyard on the campus of the College of Charleston, a burly state trooper had just the opposite feeling. "Oh, I'd say there's quite a bit of excitement around town.I never did see this square so packed with folks. I'd guess there was maybe 5,000 of 6,000 when it started."

My own estimate, and later counts by festival officials, would put the figure at half that number. Inclement weather may have cut the turnout some, though the rain, much needed here after months of drought, magically stopped during the inaugural festivities and didn't resume until the hour of speeches and music was up.

If the audience for the lauching was smaller than expected, the press attendance had been a surprising deluge. Critics had reporters from virtually every major city are showing up, plus the national magazines and the networks. Walter Cronkite is here, and so is The Wall Street Journal, along with Italian and German broadcasters, the New Yorker and the Voice of America.

Public television is present in force, taping material on the festival as a whole, and also last night's opening operatic performance of "The Queen of Spades."

For 12 days, Spoleto U.S.A. will offer a jam-packed roster of opera, concerts, play, musicals, films, exhibits, lectures, receptions and tours, including the world's premiere of aplay by Simon ("Butley") gray and a major dance gala on "Scriabin Day," June 4. So far, about half the tickets put up for sale have been sold. Contraryto rumor and some published reports, hotel space is amply available although many of the prime spots are full.

one senses a certain ambivalence among Charlestonians about the event. The News and Courier, the local morning daily, boxed the Spoleto story in red at the top of Page One, and led off by nothing that the festival "has critics, politicians, and press across the country sitting up and taking notice."

The pride, however, is mixed with a measure of anxiety. Perhaps the first thing on everyone's mind is, can this work? Can a tranquil city 70,000 with cultural life of its own sufficiently magnetize festivalgoers across the city and nation?

But the same amount of concern goes into the question of what happens if it does succeed. The glory of Charleston is its untouched surface, the serene elegance of its cobblestones, stately houses and churches, exquisite porches and gardens, all speaking of a past in suspended animation.

If the festival brings in the hordes year after year, will it affect the unique quality of Charleston as a place and a way of life?

The official opening was pleasant and unpretentious. There were brief addresses by the bigwings, including among others, Menotti, festival music director Christopher Kneene, Mayor Joesph Riley Jr. of Charleston, and Nancy Hanks, chairman of the National Endowmentfor the Arts, which has helped support the event. Then there was some unmemorable music-making by the Spoleto Festival Brass Quintet, much of it inaudible in this setting.

South Carolina's Gov. James Edwards summed up the hopes of the instigators: "This event will mark the beginning of the Charleston becoming the cultural center of the performing arts, at least for the Southeast, if not the whole United States."

Around town, though, and on the local TV talk show, attention was focused on an Esquire article about Charleston by critic Albert Goldman who called it "the Sleeping Beauty of American cities? and wonders if something like Spoleto can rouse it from torpor. It's a classic case of a cuty's 20th-century growing pains, exacerbated by unexpected limelight.