The United States needs to make cuts in foreign military spending, but we should still keep defensive measures alive. A lot of that spending is due to American military bases around the world, many in places that have not seen war for decades. We need to shut down these bases because they only cost us money and make local civilians angrier with America- it is part of the reason why many people around the world have a negative opinion of this country.
Interestingly, there is also a link between our military bases around the world and terrorist attacks. Robert Pape wrote an excellent book on the matter in which he examined every suicide terrorism event in the last 2 or 3 decades and came to the conclusion that the primary reason for most of these attacks was the presence of foreign troops in countries from which these terrorists are from. There was a stronger connection between foreign troops in one's nation and terrorism than there was between religious fundamentalism and terrorism.