This was a proclamation that was created in order to prevent people from crossing over to places wherein they have no right to be. The French and the Indians were still going through the war at that time. When this was released, it caused colonists to fear the continual British restrictions to their own rights.
This actually has a lot of effect on the Americans as Britain was able to get a large percentage of the North American land. While this was supposed to lessen the conflict between people, it is safe to say that not everyone was happy with this proclamation but at that time, they had nothing else to do but to honor it.