Saddam Hussein operated on similar assumptions about American political will to absorb casualties until his army got blasted in 1990 then desposed in 2003.

Subsequently, most potential enemies will be operating in the grey line between doing some damage to American interests while not so much that it pisses them off to really invade. Conversely, the US military does serve as a deterrent that heavily limits the actions of opponents from actualizing their own goals. Instead they need to engage in decades long asymmetric warfare while their population suffers without a end goal in sight. And even while USA might be unwilling to engage, it dosent stop other opponents like Israel with more political will from performing more direct actions.