The bold Americans

It is a bold word, Americans, in the context of our National Portrait Gallery, even impertinent there when we recall the Boston Tea Party and its consequences. It stands alone as the title of the gallery's current exhibition - sans the, sans great, sans heroic, sans historic - just plain Americans. Nor is there a subtitle - not The Makers of a Nation, not From Washington to Bush, not From Boston to Baghdad, not From Independence to the Most Powerful Nation the World Has Ever Seen - just plain Americans, a word so loaded with excess in war, wealth, commercial colonisation and cultural imperialism, so supported by the propaganda of its film industry, its musical comedies and its literary tradition, that it can stand alone and make the rest of us stand in awe, but an awe that is for many of us grudging and sceptical.

Americans are they who without conscience stole a continent and gave it a European name, whose gifts to the indigenous peoples were wholesale slaughter and the deprivation of their culture. Americans are they who drove their new continent's wild animals and birds into extinction and who ravaged and scarred an unspoiled land for its natural resources. Americans are they who, as intellectually and emotionally conditioned as any communist, fascist or zealot of Islam, believe that not only has God uniquely blessed America and all that Americans have done to it, but given them the right to extend that blessing wherever map-makers have drawn their lines of latitude and longitude; we have, in consequence, McDonald's in Port Moresby and Coca-Cola in Tashkent.

John Updike, writing in the exhibition's catalogue, argues that "Americans took root by an effort of will" - and so they did, but that effort of will was expressed in ethnic cleansing right across the continent, in wars of territorial expansion against Mexico and Spain, in a century of slavery, in two centuries of prejudice, and in the unfeeling imposition of gross industrialisation on what had been an ancient Arcadia until they came.

What, then, should we expect of American portraits of themselves? Images of swashbuckling and swagger, of wealth, power and confidence, of bravado, bombast and success, audacity and bumptiousness, amourpropre, the thick skin and an odious sense of moral righteousness? Yes, all these, for anyone who has seen American portraits in American galleries and other public places there will recognise this list, larger than life, the idiom unmistakably European, but the subject, his status and persona inflated beyond European scale; just as American neoclassical architecture is the superhuman apotheosis of a European style (and very good, to boot), the way that Americans memorialised themselves had to be apotheotic too.

With such an expectation, the NPG's current exhibition is something of a disappointment - but for that, as the choice of pictures was not the gallery's, its authorities must be forgiven. It seems that the American equivalents in Washington, closing their own NPG for refurbishment over the next four years, have volunteered the loan of 70 paintings and 58 photographs that, in spite of presentation skills cleverly exercised in organising the material, seem less a logical exhibition than a random ragbag choice.

This would, perhaps, matter not at all if the pictures were great works of art and portraiture, but these are terms that stretch to very few, if any, and the exhibition is remarkable more for its odd fish and curiosities than its minor masterpieces. It includes, for example, a portrait by Degas of Mary Cassatt, far and away the best of women painters in her day, that she sought to prevent her family and friends from ever seeing, so much did she dislike it. We can easily see why, for the composition is so startlingly awkward and the face so uncomfortably disproportionate within it, that even Degas, master of informality, could not pull it together and left it messily unfinished; an interesting document it may be, but very little more.

Among the early things, some of them as bovine and provincial as the local portraits of the north of England, are two unfinished studies of George and Martha Washington, by Gilbert Stuart. They are unfinished in the sense that these two faces confront us from 4ft canvases that are otherwise bare, but the faces themselves, painted from life, are finished to such a high degree that Stuart kept them as the benchmark for the copies and variants that he would inevitably have to make.

The liveliest thing in this section is a small self-portrait by John Singleton Copley, an image so dashing that it could be French, and so sensually perfect, so lovingly narcissistic that it is quite indecent for a man of 40. Painted in 1780-84 (so they say), nothing quite matches it for startling quality until, after a slow plod past poor things of worthy philosophers and authors, virtuous statesmen and stolid generals, we come upon Whistler, looming large and black against the Thames, by Walter Greaves, his Chelsea boatman acolyte, in 1870.

Nearby hangs an equestrian portrait of "Little Phil Sheridan", General Ulysses Grant's favourite cavalryman, plump as a pudding on a wooden horse in 1871, of which Thomas Eakins (an exceptionally fine painter when let off the leash) remarked, "I never in my life saw such pretension united with bad work. You could not sell such a picture in Paris for three francs." He was right. It is preposterous.

Eakins himself is represented by a bust-length portrait of a forgotten journalist, his view of him intense and penetrating, but far from the single picture with which, in a mixed exhibition, one of America's great painters should be epitomised. But the whole of this section is stricken by a doldrum, with John Singer Sargent in commercial mode; John White Alexander imitating Whistler but failing in the borrowed affectation; Stanton Mac-Donald-Wright attempting Cezanne with a gaudy, vulgar, note; Lee Simonson cobbling together halfa-dozen post-impressionisms; and Philip de Laszlo at his melting-butter worst.

In this largely pre-First World War group only one picture is outstanding, and even that is dull by the painter's customary standards: it is a three-quarter-length of Nelson Aldrich, statesman, by Anders Zorn, a Swedish painter once famous in England but now entirely forgotten, whose reputation deserves examination, if not revival - though "too many ridiculous fat nudes" will probably be the verdict if it ever happens.

In the 1920s, the descent continued, gathering pace in succeeding decades with each ill-digested, modern mannerism wiping out the one before and imitation piled on mimicry, until the exhibition ends with Warhol, prescient, printing Michael Jackson's portrait pink and pale - did art inspire that dark complexion's change?