LONDON - Remember the G-2? America's financial difficulties and foreign entanglements, together with China's economic ascent, led many last year to envisage the emergence of a sort of global condominium between the two countries. The G-8 had morphed by necessity into the G-20, which, whenever it really mattered, would shed its zero: the United States and China would call the shots. The idea was an over-simplified reflection of global realities. It left out other emerging powers like Brazil and India. It exaggerated the weakness of America, which remains the world's only superpower. It also reeked of the European Union's peevish realization that its inability to get its act together on contentious issues was likely to place it firmly on the sidelines.