There are a number of ways in which you could say that politics have affected population patterns in the United States. Let us look at two of the most important of these ways.
First, you could say that politics has helped to determine which areas of the Americas have attracted immigrants. This is not the only factor, but it is one that has had some impact. For example, in the 1840s, many Germans left their country for political reasons. Many of them came to the US because of its tradition of political openness and freedom. Specifically, they came to the North in part because the South had slavery, which they did not like.
Second, you can say that politics has affected which areas within countries have become populated. Again, politics is not the only factor. However, we can say that some political systems are more centralized than others. When you have a political system in which the government is of paramount importance, people will want to come and live where the government is seated. This attracts large populations to political centers like Mexico City.
Thus, politics has helped to determine which countries people live in and which areas of the country are more populated.