The difference between conventional war and unconventional war is the overall objective. Conventional war is the destruction of another state's ability to wage war. Once that has been accomplished, if war continues, it's unconventional, because it has to be waged by non-state actors.

States hold war materiel and personnel on military bases, these weapons have long supply chains and generally cannot be hidden. Once you've blown these things up, then the state cannot make war any longer.

With aircraft, missiles, satellites, AWACS, advanced intelligence capabilities, the expected speed of conflicts has gone from days to hours in the last few decades. The US enjoys complete dominance over the rest of the world's militaries. There is no state, no imaginable alliance of states that could withstand a full-scale US military attack. We'd destroy their air forces, naval forces, and any ground forces they could muster within hours.

So long as we refuse to fight an unconventional war, then our troops could just go home. It's because our leaders get cocky and idealistic that we get dragged into ongoing guerrilla conflicts.