And it's important to note that "Star Fleet" was in existence before the creation of the Federation, which would set the tone for the culture of Star Fleet.  In the 1960's, the parallel to the Star Trek Earth was of course, the United States.  The UN is located in New York as the Federation was located on Earth and at that time (and still, for that matter), the U.S. was generally the Big Stick for various confrontations around the world.

The interesting question is this:  In TOS, there were rarely more than shuttles or small transport ships from other species within the Federation.  Are we to assume that the Vulcans, Andorians and Tellerites disarmed and dismantled their capitol ship fleets?