Good Americans go to Paris when they die, bad ones stay in America, joked Oscar Wilde, a quip that both satirised the transatlantic idyll of bohemian Montmartre and predicted the fate of the American artists in it. The National Gallery's gorgeous, luminous Americans in Paris is a stunner from first to last but, for all the intrigue of fresh works by lesser-known names, three artists tower above everyone else, and they alone are the ones whom 19th-century Paris accepted during their lifetimes and made immortal afterwards: James Whistler, Mary Cassatt and John Singer Sargent.
So well integrated into artistic Paris were this trio that we think of them as honorary Europeans. Whistler's "Arrangement in Grey and Black No 1", depicting his mother, is the most famous American portrait but lives in the Musée d'Orsay, reigning supreme among the symbolists there as "un peinture de convalescence", in the words of J.K. Huysmans. Sargent's "paugh-traits", too, are chronicles of the privileged Europe that dis-appeared with the first world war, while Cassatt, close friend of Degas, was the sole foreigner and sole woman to exhibit with the impressionists. Her starry painting here of a tea-drinker in salmon-pink tulle with lavender gloves so exquisitely sums up the French leisured class that Huysmans singled it out for its "fine odeur d'élégances parisiennes".
Yet put these artists in context, as expatriate Americans whose story is the subject of this intelligent, far-ranging show, and you see that it was the meeting of Old World with New that conferred their distinct flavour and tonal range. Cassatt, in what is almost a mini-retrospective - enhanced by a display of herJapanese-influenced prints in the Sunley Room - emerges fascinatingly as an impressionist who developed her own American idiom, balancing immediacy and a bold pictorial design indebted to Degas' cropping, framing and powerful diagonals, with a Bos-tonian grace, ladylike but vigorous. A father sunk in an armchair with his son perched alongside, their dark suits fused into a black mass emphasising their affection as they read a paper together; the flushed cheeks and pale back and shoulders, reflected in a mirror under a chandelier's sharp glare, of the eager theatregoer peering from her loge; the pause in conversation in "The Tea", one woman holding her cup with cocked finger as she averts her eyes before answering her friend, in an intimate atmosphere heavy with the weight of a shiny silver tea service and the confining pattern of striped wallpaper: unerringly, Cassatt distils the subtleties and pleasures of social moments with the chaste, east coast precision of Henry James.
Cassatt, like many artists here - a third were women, shaping this show's domestic emphasis - arrived in Paris in the 1860s. Many of her compatriots came from provinces with no art schools and the opening, focused on Sargent's lively, darting portrait of the hypnotic Professeur Carolus-Duran and ThomasHovenden's Bohéme-like "Self-portrait of the Artist in his Studio", with dashing moustache, pink cravat and violin, beautifully evokes their intoxication with the trappings of atelier and classroom. Yet more rapturous are the impressionist scenes of everyday life into which the new arrivals flung themselves. Childe Hassam's "April Showers, Champs Elysées" and "Along the Seine, Winter", have the empty foregrounds, dramatic perspectives and staccato brushstrokes of Pissarro and Caillebotte. The decorative trellis of leaves, treetrunks and slats of a bench in Maurice Prendergast's "The Luxembourg Gardens", and his jewel-like panel of seven scenes of girls floating through the park, "Sketches in Paris", recall Bonnard's delicate surfaces. Sargent's early virtuoso painting of promenading lovers, "In the Luxembourg Gardens", its flickering, purple twilight dotted with stabs of red - darkening flower beds, the woman's fan, the man's flaring cigarette - is heartbreakingly beautiful: a precocious contemplation of time and memory.
A handful of the newcomers took what they needed from Paris - weightiness, form - and returned home to forge the beginning of a characteristically American style, uncompromisingly realistic and emphasising wide-open spaces: Winslow Homer's tumbling dark sea and heavy, loping figures in "A Summer Night"; Thomas Eakin's macho river scene "Starting out after Rail". But they are exceptions: mostly the insecure Americans fell into a homage-and-imitation of Monet and Renoir that turned conservative when (for they rarely stayed long in Paris) transported home to Philadelphia or Boston. The result was a nostalgic, sun-drenched impressionism that persisted extraordinarily long in America and today offers a frisson of almost illicit,counter-historical joie de vivre. The light playing on the frothy pink dress and awakening features of Frank Benson's 17-year-old daughter "Eleanor" as she contemplates a shimmering Maine garden, for example, was painted in 1907, year of Picasso's "Demoiselles d'Avignon"; "Allies Day", quivering skyscraper-stage of impressionistic red, white and blue flags, signifies - note the tricolore - Hassam's lasting debt to Monet, but dates from 1917, by which time Europe had already worked through cubism.
Blazing above this derivative mêlée like fireworks, the individualists Whistler and Sargent turn on a conscious negotiation with European tradition, and their contrasting responses form the thrilling central tension of this show. Whistler, older by 20 years, was the pioneer. Radically simplified seascapes such as "Harmony in Blue and Silver: Trouville", and portraits of his mother and of his girlfriend in "Symphony in White", have the flat, strict surfaces and desolate loneliness of 20th-century American painting - anticipating not only abstraction, as their aesthete titles suggest, but also Hopper and even Warhol. James mused on Whistler's "thin empty lovely American beauty" and Don de Lillo noted of "Arrangement in Grey and Black" that tiny, pinched old Anna Whistler in black, staring at nothing, is "a figure lifted out of her time into the abstract arrangement of the 20th century, long before she was ready". Yet she is also rooted in Velázquez, the hero Whistler shared with Sargent.
"Madame X", the monumental portrait of the notorious southern planter's daughter Madame Gautreau, was Sargent's res-ponse. As haughty as any Velázquez monarch, her head crowned with a tiara shaped as a crescent moon - symbol of the huntress Diana - and wearing a sweeping décolleté black gown to offset what the painter called her "uniform lavender or blotting paper colour" skin, this American social and sexual predator turns disdainfully from the viewer. Sargent has caught every nuance of her ambivalent position in Paris: jarring accent, jangling nouveau manner.
Where Whistler the outsider questioned the grand European portrait, Sargent the outsider embraced it - with a fervour that no knowing home-grown European artist, at a time when the tradition was clearly bankrupt, could have managed. That is Sargent's brilliance and his limitation, but it is the dazzle that holds sway here. His greatest portrait of all, "The Daughters of Edward Darley Boit", makes a rare trip across the Atlantic and is alone worth the price of a ticket. In an opulent but cool Paris interior, the girls are dwarfed by the enormous blue Chinese vases in the family's rented hôtel particulier. The youngest, in luscious white, sits on a rug with her doll, suffused by sunlight. The next child, smocked in more sober cream, stands at the painting's edge as if wanting to flee. The older girls at the back are in shadows that tone down their white dresses; one sulks, the other has a faraway, emotionally absent look. Beautiful, wealthy and destined for a sadness that Sargent has intuited - none married and two later suffered mental illness - they look like lost orphans: homesick innocents abroad, sacrificed to their parent's dream of Paris, and a metaphor surely for the clash of American innocence and European experience that fuels Sargent's oeuvre and is the subtext of every work in this wonderful show.
'Americans in Paris', National Gallery, London, to May 21, tel 020 7747 2885. Then Museum of Fine Arts, Boston, and Metropolitan Museum, New York
