CONSTELLATION Brands, one of the world's biggest winemakers, has booked $US100 million ($A107 million) in impairments against its embattled Australian wine business and warned of flat growth in the United States this year as high unemployment saps sales at restaurants, cafes and pubs. The owner of local winery BRL Hardy, as well as a portfolio of popular international beer and spirits brands, said on-premise sales in the US were hardest hit by the economic downturn, overshadowing improving wine sales in Europe and early signs of a possible end to the crippling grape glut in California