While there has been no missile defense system, no rockets have been launched against the United States. Zero. None.

That has got to be the oddest rationale for not taking a precaution that I have ever heard. Now, if no nations actually possessed missiles that could threaten the U.S., or if no nations were actively developing them, particularly one or two with a somewhat suicidal culture, you might have a point. As it is, you sound like someone who won't lock their car or house in a crime area because they haven't been burglarized yet.

Incidentally, part of the goal of developing missile defense systems is to be able to provide it to nations that are a bit closer to the threat zone than we are.