The FTSEurofirst 300 index of top shares closed Monday up 0.7 percent at 1,090.29 points, the highest since July.
Koehring said the risk of contagion from Greece to the rest of the eurozone had lessened during the past year. That's in part because of intervention from the European Central Bank, banks' own deleveraging policies and progress in Italy and Ireland. But there are still major risks.
He said allowing Greece to default would have caused major losses among European banks and could raise fears among investors that Portugal or Cyprus, or both, could be next, "thus potentially raising the need for further bailouts for other highly indebted countries too."
U.S. businesses, even without direct ties to Europe, have seen their investments suffer from a volatile financial environment. The value of the U.S. dollar has also been affected by the fluctuating euro.
While the U.S. stock index levels of 1,300 and 13,000 might be celebrated among some investors who see gains in their own portfolios, they might have little relevance for the U.S. economy.
"The economy continues to operate far below its potential, which means that an extended period of above-trend growth is needed to mop up current slack," Brown wrote in a note to investors.
Nevertheless, the U.S. unemployment rate fell to 8.3 percent in January, the fifth monthly decline for the jobless figure. Retail sales rose 0.4 percent in January, which included strong automobile sales.