American fashion used to be a poor relation of Paris, but those days are over. The reliance of United States designers on hand-me-down ideas from their European colleagues has been lessening with each season. Instead, with growing confidence, the Americans now bring their own protean talents into play.
This developing sureness was again evident here recently during the second of two hectic weeks of showings for next fall and winter. Scores of Seventh Avenue houses displayed thousands of fashions, which were viewed not only by the national press and retailers, but also by their peers from abroad. Contingents of reporters and buyers from Japan, Britain, Scandinavia, and France have been attending the openings for several years. This time, Italy sent 10 editors and photographers from leading newspapers and magazines -- an unusually large number. That in itself is an indication of the burgeoning importance of American design.
Media coverage tends to center on the major collections -- the ones by the big names that today are known around the world. Although a lot of new clothes in these collections cater, as they always have, to expensive tastes and impressive bank balances, the message inherent in them are not ''leisure class only'' but have universal application.
The directional signals for next season at Geoffrey Beene, Oscar de la Renta, and Bill Blass -- three designers who presented their fall fashions in the second week -- point toward longer clothes (both narrow and full skirts are shown) for daytime, and shorter styles for dinner and dancing hours. The overall emphasis is on handsome-looking clothes that have a reasonable amount of built-in longevity and -- with the exception of hip-girdling and ultra-full bubble shapes -- do not make a travesty of the natural lines of the body.
The suit, the dress, and the coat are given due respect as integral elements in a well-balanced wardrobe. Such extraneous items as the trailing shawl have been put to rest. The extra outer wrap is likely to be a more easily controlled stole in a matching fabric, or a removable capelet. Cape and puritan collars are , in fact, everywhere, on dresses and blouses particularly.
Coats have roomy armholes, even such modified princess styles as those shown by coat-expert Ilie Wacs. Dolman, kimono, and raglan cuts are popular. Shoulder treatments, while generous, are seldom bunchy with too much gathering, nor over-thickened with too much padding.
Suits have jackets that often close at the neck, thus protecting the throat in chilly weather, and they are semifitted at the waist and loosely belted. The lines are uncluttered, and the fabrics mostly thin tweeds in dark earth tones. The exceptions are the gray flannels, blacks, and the camel flannel with oversized window-pane plaid at Bill Blass. The practical idea of the ensemble of matching Inverness cape over a suit was revived in a series of Donegal tweeds by Oscar de la Renta, who also showed a spectrum of tattersalls, herringbones, and Prince of Wales checks with sumptuous silk Jacquard blouses.
Where the clothes would be worn has also been taken into account. Vera Maxwell, who stressed the coat with the matching skirt in her collection, commented that this combination will carry a woman through practically any situation, wherever and whenever, provided she is equipped with an assortment of blouses. Numerous semitailored dresses (many have white wing collars and black floppy bow ties) are offered as answers to the working woman's prayer. If Oscar de la Renta chose to make his executive-suite turnouts of costly cashmere, well, no matter, at least the thought was there. Lower-priced versions will no doubt surface eventually in his ''Miss O'' collection.
The pragmatic approach, said to be an American trait, extends to the use of lightweight fabrics that move with ease and are comfortable to wear. Geoffrey Beene's handling of sheer wool challis, often surprisingly banded or inserted with lace (and worn with lace stockings), or bound at the neck with an edging of snakeskin, is done with special grace and admirable restraint.
There is nothing else quite like Beene's compositions of below-calf peasant skirt, curved short jacket, and simple top. They are assemblings of various rich fabrics, related in color, texture, and print in ways that only an artist would see. Patterns break patterns; laces are enriched with satin or glints of glitter. Quilting, multiple pipings, inventive placements of appliques, and hints of metallic (chiefly in late-day clothes, where metallics are mostly found in the new fall fashions) are used with startling virtuosity.
One designer has said that his work has been affected by the time he spends every year in the Orient: ''The Japanese approach to design seems to be essentially one of elimination. The excessive, unmeaningful parts are simply discarded.'' The same influence could be detected in other collections. The dresses at Albert Nipon are now sometimes a T-square cut. When one of the models at Pearl and Albert Nipon's presentation held out her arms to show the satin flower pattern on the back of a Jacquard gown, the look was that of a rare kimono displayed on an Oriental T-shaped stand.
Not every American shopper is drawn to understated clothes, especially the party-goers. The designers who dominated the first week of showings -- Calvin Klein, Ralph Lauren, Perry Ellis, and Donna Karan and Louis dell'Olio of Anne Klein -- stressed the glory days of British country sportswear, laced with plenty of black-tie-tuxedo dressing for evening. That kind of no-frills or few-frills fashion does not satisfy all and sundry.
To fill out the picture, Bill Blass and Oscar de la Renta offer enough big-time-ball gowns to populate every dress-up charity event from coast to coast. The most beautiful of the Blass satins, velvets, and matte jerseys have back drapery that frames bared-to-the-waist decolletages, reminiscent of 1930s belles who once graced the pages of old Vogues. His Texas and California customers will, however, be apt to crave the flapper dresses and long slinks that are paved with rainbows of paillettes in the ''give 'em the old razzle-dazzle'' manner.
La Renta's largesse comes in the form of changeable taffeta bouffant dresses with huge sleeves and infanta necklines, all of which seem suitable for the grandest of grand occasions. The sort of solid gold bullion embroidery sparked with jeweling that Indian maharajahs and their consorts wore in state encircles the waists and the bodices of black velvet dresses, and also covers an entire jacket. Affluent, conspicuous consumption, it appears, is ever with us.