Whether we like it or not, we have sunk a great deal of money and blood into Iraq to first, depose Saddam, second, to drive out extremists, and third, to install some semblance of a functioning government. To pull out now would be to send a green light to extremists all over the world: they can overthrow legitimate governments, pillage their cities, and execute opponents to their liking with absolute impunity.
Keep in mind, ISIS are not your average Jihadists. They are well organized, and will use brute force to achieve their end: an old style Islamic Caliphate. Without our help, we will be negotiating not with a prime minister but with a Caliph. The Iraqi armed forces need urgent assistance, or they will be overrun.
Yes, the United States should send military aid to Iraq, because we are the ones who got involved there in the first place. It would be unfair for us to leave them on their own now. Their people are suffering. They need our help, and we are responsible, since we put their country into upheaval.
No, the United States should stay out of Iraq because it is not their war to fight, nor are they actually helping. Tax payer funds and resources should be kept in the country to aid in internal affairs rather than be sent overseas to fight in a war that does not concern the nation.
While the images coming out of Iraq at the moment are heart wrenching, running in to save the day once more will not solve anything. Iraq needs to learn to protect and stand against these groups themselves, otherwise the rest of the world would be at their call forever, and the problem wouldn't be solved. Supporting them is one thing, but their own troops are what should be used.
The United states is in a spot between a rock and a hard place with their situation here. They must yes impose their will in the countries in the middle east that our consider radical, but they must their lesson. The US has spent too much of its finances and willpower on Iraq and other Middle East countries with null change in the situation.