Depends on who you ask. In Iraq, we do not look that bad. We stuck around and are winning. In Afghanistan, there are numerous problems, many of which involve other countries that we need to be involved in. In a world of "non-intervention" this would not be possible.
This begs the question, if we 'do not look that bad' in Iraq, what would qualify as 'bad'? Afghanistan was not an instance of intervention, it was a defensive war. Al Qaeda was effectively a state-sanctioned entity in Afghanistan. Once it was determined that they were responsible for the Sept. 11th Attacks, we were well within our rights to defend ourselves.
If you study the terrorist ideology, staying in Iraq was 100% the correct move. If you want to make it a credibility issue with our allies, staying was 100% the correct move again. These are all major issues.
'Staying' was not necessarily a mistake...Going in initially, however, was a massive mistake.
Further, if we put the military on the Mexican border, you can be assured immigration would abruptly end. Although, in a "non-interventionist" world we would have to just sit there and accept the situation in Mexico with no options.
Our options are to enforce immigration laws. I don't propose intervention; Mexico is a sovereign nation that has not taken aggressive action against us.
In a non-interventionist world we would be unable to interdict ships carrying nuclear material from North Korea to other rouge states. In a non-interventionist world we would stop being non-interventionist when one of those weapons obliterated an American city.
If we had been non-interventionist for a reasonable period of time prior to this date, there would be little reason for a 'rogue states' to want to nuke us.
And yes, in many cases defense involves being proactive. You can call it aggression as you choose, but being proactive to ensure security is defense.
I recognize the difference between being pro-active and aggressive. We can justly fight a pro-active war, we can not justly fight an aggressive war. Your examples of the seizure of nuclear material, out of context are examples of pro-action. If put in the context of our interventionist foreign policy, it's less clear. Now, that said, if we are engaging in an interventionist foreign policy [which we are], we
have to take action such as what you described.
And we should secure our borders, but that should not simply be the main focus of our defense posture. If it is, then we will no longer be the dominant world power, and we will face massive proliferation, and increased risk of a catastrophic terror attack.
I'm personally unconcerned with 'dominance'. Security is tantamount [from a foreign policy perspective]. A country does not need to be the 'dominant world power' in order to be secure. That is the difference between non-interventionism and a borderline neo-imperialist foreign policy. We don't settle for 'safe', we need to be 'dominant'.
-NC