What people know is often more an issue of affect (emotion) than it is cognition (thinking). Attitudes about the U.S. by people in other countries are obviously a function of both, with current events sprinkled in to explain variation over time.
From 2007 to 2008, opinions about the U.S. have improved in such countries as South Korea and Tazania but gone down in Japan and Mexico.
People from Turkey have the least favorable views of the U.S., according to the Pew study. South Koreans give the U.S. the highest marks, with 70% saying "favorable."
All of these are susceptible to their own economic conditions and however the U.S. has either screwed up or succeeded in their backyard of late.