What is it about Iraq that would make that true that was/is not true about India/Pakistan, Austria/Germany, N/S. Korea, Yugoslavia, the Soviet Union, or even Israel? Would Israel be better off if it were to be absorbed into a greater Palestine under Arab control so the various factions could "work together"?
Dividing India and Pakistan was a mistake. Or do you not recognize the constant state of low level warfare between the two countries? They're both nuclear powers now too, which only makes things worse.
The situation in Germany and Austria is different. It cannot be used as a model for what is proposed for Iraq by Biden.
North and South Korea are still technically at war. It is the DMZ and our military presence that has kept the peace there.
I'm not so sure you can argue that what happened to Yugoslavia is a ringing endorsement for Biden's plan.
Palestine would do a lot better to be absorbed into Israel than to suggest that the process be the other way around. We're talking about absorbing the three distinct factions in Iraq into a single, cohesive, and democratic government. The key is the "democratic" part. What we have in Palestine is the result that we want to avoid in Iraq, and which is what we'll get in Iraq if we create a loose confederation instead of a strong central government. If anything, Palestine should be all the proof we need of what will go wrong if we go along with Biden's plan. Israel should've just declared that it owned Palestine and annexed it back when it won those lands from its neighbors.