London (AFP) – The coronavirus threatened Americans with their hardest week in memory on Monday and put Britain’s prime minister in hospital, despite early signs that some of Europe’s hardest-hit countries may be turning a corner.Japan announced an imminent state of emergency and a trillion-dollar stimulus package, after the US surgeon general compared the likely impact of the epidemic in the week ahead to 9/11 or Pearl Harbor.But it was a more mixed picture in Europe, where countries already ravaged by deadly COVID-19 outbreaks reported lower numbers of new infections and, in Austria and Ital…