They aren't bumbling idiots though they come across as one . Most times they invade for one set of reasons & quit without having accomplished what they set out to leaving neighbouring countries to clean up the mess or live with it.
And they've been doing so since the end of WW-2 - the principal reason being the same as Admiral Yamamoto declared why the US can't be defeated by Japan before the latter undertook Pearl Harbor arguing against the war which was shot down by the dominant faction then. The reason is as simple as a country , any country defeating the US by invading it & marching upto the WH.
Since no country's in a position to do that , the US doesn't exactly give a damn before initiating the next conflict. We're counting on China to change that while going down themselves.
To return to your previous proposition of the US tying all loose ends up - quite frankly I don't see Putin out of power & even with the N option gone I don't see the mullahs out of power even if the US wants & is doing / will do everything in its power to dislodge them.
With these entities still around how have you tied up loose ends ? The moment the US is distracted which it will be since it has spread itself thin , they will be back like bad pepennies.
