The reality of human nature is that successes encourage, while failures discourage.
The reason the US has gotten bolder in recent times is not just because of desperation, it is also because it has seen great results from its new doctrine of quick, precise, and most importantly cheap decapitation strikes.
The ghost of Iraq and Afghanistan haunted American interventionism for twenty years. The failures of American nation-building, the trillions spent, the tens of thousands dead, and from a political perspective, the repudiation of Bush and all those associated with him, caused serious face loss for the neo-conservatives in Washington. It made future presidents timid about sending troops into a foreign country and so we saw an overall decline in US interventions for nearly twenty years.
But that's starting to change. A new military doctrine is emerging - in Syria, in Iran, in Venezuela, and arguably even in Ukraine, where the US is combining well-orchestrated, "light touch" precision strikes with heavy intelligence support to achieve more limited political and economic outcomes on the cheap. Sure, you might not be able to get a local base or "modernize" the country to your liking, but you also don't need to spend decades of time and trillions of dollars just to have the country end up working with the Russians and the Chinese any way.
This is not exactly a new doctrine - the concept of limited scale, intelligence-driven operations has always been in the arsenal - but it seems to be making a come back off of three things: 1) new technologies (or technological disparities, to be more exact) that enable more comprehensive denial of a nation's ability to fight back without lengthy, expensive bombing campaigns, and 2) decades of experience conducting precision operations in the Middle East, where the US military had to learn how to do things with a light touch the "hard way" because the shock & awe doctrine wasn't working, and 3) new-found political culture where "total victory" is no longer the goal and cutting losses early is completely acceptable.
Overall, I'd say it represents a return to form for US interventionism and the neo-conservative establishment, and if proven to be sustainable, can serve as the basis of a new grand strategy of "intervention on the cheap." Of course, the rest of the world will adapt to this, and ultimately it only takes one catastrophic failure for us to go back to step one.