Your point about poverty is of course correct.

You're conflating two very different situations in regards to Iraq. It's not one Iraq forever war.

There's the Iraq war (Second Persian Gulf War), and there's the Iraq civil war. The Iraq war, versus Saddam's regime, ended very quickly. That war was won trivially. The US could have optionally left at that point if it just wanted to declare an easy victory. Civil wars can go on forever (and given Iraq was a forced together nation of three major groups that dislike each other, it's likely going to).

The US achieved its primary goal in Afghanistan very quickly as well. It wiped out nearly all the organizing and attack projection capabilities that Al Qaeda had in using Afghanistan as a haven. The primary objective was not to kill all the Taliban. The Taliban was a different, optional objective. Afghanistan, like Iraq, is now a civil war between multiple factions that all want power.

Hence "cycle of violence"; the US launched its second invasion of Iraq, starting the war. It then declared victory and eventually left, having defeated and disbanded the conventional army of Iraq - but that did not stop the fighting. Car bombs are stil regularly going off in Iraq.

> wiped out nearly all the organizing and attack projection capabilities that Al Qaeda had in using Afghanistan as a haven

It's questionable as to how much they had in the first place ... and yet, Al-Nusra, an AQ-derived splinter organisation, is now fighting alongside US-backed groups in Syria. https://www.theamericanconservative.com/articles/are-al-qaed...

We even now have weird indirect US-Iraq-Iran cooperation against ISIS. https://www.chathamhouse.org/sites/default/files/field/field...

> end the cycle of violence with bombs

Worked post WWII most places.

Really only for Germany and Japan, only because those were state-led wars. Not for any of the subsequent conflicts; Korean war isn't even really over yet.