In the context of aggressive foreign policy where we bomb the shit out of people… They are probably referring to how in the 1910s USA was stumbling through an incursion into Mexico to fight rebels / raiders. As we joined WW1, some saw us as a rowdy militia, like cowboys. We had to borrow materiel because we weren’t yet a proper war-machine like European countries were. Exactly 100 years ago that wasn’t the case though. Yet there would still be quite a ways to go until the era of “top 3 air forces” and super carriers patrolling the globe while drones blow ‘terrorists’ to smithereens.