With Ron Paul in the White House, I would not be in the least concerned about our nation defending itself against an attack. Rep. Paul voted in favor of the Afghanistan resolution in the aftermath of 9/11, and simply because he doesn't embrace every neocon wet dream military intervention doesn't make him weak on defense.
He believes in the original intent of Founders like Washington, who didn't believe in excessive foreign entanglements.
Having said that, Rep. Paul does need to nuance his rhetoric in the realm of national defense, given that so many are apt to misconstrue him. But he simply is not a neocon, and never will be, and I don't have a problem with that.
People need to understand that they will never find any politician whom they agree with 100%. Ron Paul is only one man, and if he got to the White House, the odds are that, after being adequately briefed, his national defense policy would probably become a bit more "hawkish", just like several other Presidents.
For national defense, I believe President Paul ultimately would do whatever needed to be done.