No, the role of the police in the United States has stayed relatively the same since the early 1900s and the "professionalization era" of the police. Prior to the 1900s the police did have a much different role. In the 1800s the police not only performed a crime control function, but they also performed a much more apparent social service function as well. For example, there are pictures of homeless people sleeping in Philadelphia police department during this time period.

The role hasn't changed so much, no. The tools available, as well as priorities, have indeed. There is a much more militaristic mindset among many, and access to more powerful weapons has certainly increased.

So, too, have the dangers faced increased, while the support offered by the community has decreased.