In politics, perception is often more important than reality. Do I believe that we pose less of a threat to the United States than many states within the U.S. do? Yes, I do, definitely.
I asked a congressmen in the United States whether he believed that his constituents would feel that any country, no matter how competent and whatever their intentions, could provide for the security of the United States as effectively as the United States itself. His response was that he thinks his constituents expect the U.S. to look after the U.S. The border is there and it's a convenient place to draw the line. That's where they throw the resources.
The intuitive logic is that if there are cops at the border, we'll be more secure. I would argue that the strategy being followed is making us less secure, because it is diverting limited security resources from areas of high priority. When you talk about risk management, there are areas of low priority. As a result, politics make us less secure than we would otherwise be.