We don't have a real opponent anymore.
True, but things change. Your analysis is based on the present status, the political regime presently in power (just barely). Let the left get back in power and we conservatives are not going to be so all-confident.
Imagine if the Vietnam anti-war appeaser and his party had gotten back in power. Clinton's dismantling of our military and nuclear capability would be minor compared to Skerry and the dims had they gotten in power.
In the days after WW1, Britain smug and confident, who could have foreseen the appeaser Chamberlain and the rise of Hitler in just a few years?
Chamberlain reasoned from a position of weakness. While you are correct that an extended dose of liberal leadership could weaken this nation, it would not be to the degree that would allow our opponents to gain advantage before they would again be replaced. Clinton is a great example. All he did was weaken our military to the point where it would be hard-pressed for us to kick two nation's asses at the same time, where it was then(and about to be again) a piece of cake.
It would take 20 years of liberal leadership in America for our potential opponents to gain parity with America. That is not going to happen.
Aegis, baby!