In the united states, as of 2009, which of the following was the largest and fastest-growing immigrant group

This would be the Hispanics.

In the past, the Europeans made up most of the immigrants, but the social, economical and political situation in Europe, both Eastern and Western, has improved greatly and there aren't that many immigrant from Europe anymore.

Latin America, however, still struggles with many issues and a lot of people from there look for a better life in the US.