First, we must remember that there are many countries in the Americas with very different political systems. Not all have been greatly affected by African immigration and those that have been affected have been affected in different ways. Let us look at two examples.
First, the Caribbean countries are overwhelmingly populated by people of African descent. This fact, along with their history, helps to cause these countries to feel a strong sense fo grievance against the West, which they often see as a major cause of their problems. This pushes their politics towards things like a belief in dependency theory.
Second, there are countries like the US where African immigrants are relatively few but have had a huge impact on politics. Much of our politics today centers around splits that are at least partly based on race. Our attitudes towards welfare programs are partly shaped by our perceptions of race. Almost all African Americans belong to one political party; this helps to turn many political issues into racial issues.
In these ways and others, African immigration has affected the politics of countries in the Americas.