I appear to have lost the train of thought from the initial question, but hes a few thoughts
"Divide to conquer" is a strategy that has been used time and again by despots and empires to rule over a population. Differences of all kinds can arbitrarily be used to divide people, skin color, which invisible man in the sky you believe in, origin, culture, gonades/gender, you name it. But the ultimate division is individualism, every man for himself, me myself and I. A small cohesive group will always have the upper hand over individuals even when individuals outnumber that group. You want your prey to be individualistic, the last thing you want is for a population to organize cooperate for its own common interest.
Nationalism can be good if it accentuates cooperation, pulling together, ect and bad if it is used to justify negative actions.
Empires like the British Empire and its latest incarnation the American Empire dislike nationalism when it is used by the local population to advocate in favor of the local population's interest as opposed to the exploitation of the population for the Empire's benefit.
Nationalism in Iran was bad, because Anlgo Oil interests did not want the local population to benefit from the Oil, they wanted the local population to live in abject poverty and to plunder the oil for their profit, which is why the elected government of Mossadeq was overthrown by MI6/CIA and replaced with a good old fashion brutal dictator the Shah who could keep the locals in check and rubberstamp the exploitation. The Empire thus wants local gangsters to rule over the population, the local gansters get a cut of the exploitation racket. Its similar to the feudal system, but when the banana republic's dictator is one of ours we call him a president, if hes not one of ours hes a dictator, its 'Saddam the president of Iraq' when he cooperates and wages war on our behalf, but its the 'evil dictator Saddam' when he no longer cooperates (and trades Oil in Euros instead of petro$).
"The reason our invasion of Iraq is justified, is that our specific goal is to eliminate an oppressive and unpopular dictator, who imposes his rule through force of arms, in order to replace that government with a new government, entirely created by the Iraqi people. "
Thats a cart of bullcrap, the reasons for going to Iraq were not those propagated by the corporate media and puppet politicians, more likely were Oil, petro$, Israel, etc. The US loves dictators like Pinochet, the Shah, unelected despots like the Saudi royals, as long as they favor US corporate interests, even Saddam was supported by the US, he was still a dictator then. Even the Taliban which now are the enemy-du-jour had the red-carpet reception when they were negociating the CentGas pipeline deal.