What's one more war?

Though I find it hard to believe even the Iranian regime is this stupid, if the allegation is true it'll be more grist for the "let's conquer the Middle East and remake it in our image" crowd:

An alleged Iranian plot to kill a Saudi ambassador in Washington shows that the ruling mullahs have no fear of the United States and that U.S. policy toward the Islamic republic must be more assertive, according to some Iran experts.

If the Justice Department account is accurate, the plot was launched with the approval of Iranian Supreme Leader Ali Khamenei and means Iran's leaders "did not fear a muscular American response," said Reuel Marc Gerecht of the Foundation for the Defense of Democracies, a former CIA officer.

Now, assuming the plot is genuine (something I'm less willing to take at face value than, say, 10 years ago), why on earth would Iran not "fear a muscular American response?"  I mean, between Afghanistan and Iraq, we've got about 140,000 troops stationed next door to them.  Oh, wait... they're all still a little busy.  Another 28,500 are still patrolling the Korean border, which I wager is considerably harder to cross than our own, even if we weren't there.  Quite a few others are stationed in Europe, mostly to reassure the declining powers there that we think they're still important.

So that would leave the troops at home to respond.  Problem there is it's a long trek to Tehran, and our aging air refueling fleet (not to mention most of our other favorite toys) isn't exactly getting healthier with the current operations tempo. 

It's as if we were a professional fighter in a street brawl, kinda barely holding our own against a handful of lesser thugs, while looking at bystanders and saying "you want some of this, too?"  Dumb.  After playing global Twister with our military for so long someone's bound to call our bluff... Iran or North Korea being leading candidates.  China, meanwhile, continues to bide its time while we bleed out from self-inflicted policy wounds, knowing the day gets ever closer when it can reunite Taiwan with the mainland... and we'll be unable to say a word, unless willing to use weapons involving E=MC².

Given that trend line, what's a few attempted assassination plots between longtime foes?