"who have chosen to mostly rely on the US military for their own national security"

I often wonder if statements like this are disingenuous. The US military "polices" parts of the world where American interests lie; ie Natural resources, supply chains, potential markets for American companies to exploit. When you say countries "choose" American military protection you are not considering the considerable economic pressure America can leverage when it wants something you have. In developing countries this can be a difficult choice too. By not spending on military you can spend elsewhere. Even if that means resources end up in the hands of politicians directly; which is no different to any first world country.