Hopes that the US economy has finally embarked on a significant and sustained recovery are likely to be dashed by events overseas. There is little doubt that the economy has strengthened in the early months of this year, with the consumer, industrial and housing sectors leading the way. The only weakness has been the further slowdown in export growth. But just as the spike in oil prices and disruptions to supply chains caused by the Japanese disaster derailed the recovery last year, the danger is that the knock-on effects from a Greek default will hold back the US economy this year.