Salam. Welcome to the forum. I hope you like it here. And thanks for you care for your Muslim brethren.
Ok. I will get to the topic. First of all, average sunni and shia don't have grudge against each other. For Muslims, the lives and properties of each other are forbidden to be disrespected.
And, sunnis and shias have always considered each other Muslims. Hajj (pilgrimage) is an example to that. Only Muslims are allowed to perform Hajj in (sunni, shia, sufi, etc.) Islam. And never in the history has any denomination been forbidden to perform it or forbade other denominations to perform it. Thus, the consensus of Muslim nation is that all the denominations are Muslims. Thus, there can't be enmity among the brethren in religion. (Neither among the brethren in humanity. Imam Ali says; "People are either brother to you in faith or equal to you in humanity")
But, we can't deny that, there have been seperatist extremists as well in the history and today. Who claim that anyone but themselves are Muslims, and they tend to fight others. These "people" are usually called takfiris. Their first example in the history was the cannibal group khawarij. And sadly it has been resurrected in the last decades, with names such as ISIL, Boko Haram, Nusra, etc. But, as mentioned above, they don't represent the views of the consensus of Muslims, not even sunni Islam which they claim to subscribe to. Their beliefs are the likeness of Salafism and Wahabism, but even some wahabis and salafis consider them to be monsters.
But, the point is, some politicians use this sectarianism in order to achieve their goals. Again, I repeat, the conflicts among Muslims is not out of different views. The differences have always been there. But conflicts haven't, at least not among sects. Because, in the history and today, the fights were among those who wanted to "rule" the nations rather than serving them. The most bloody wars were that of Abbasid fights. It was not a sunni-shia war. Next comes the Ottoman-Mamluk wars and repeatedly Egyptian uprising among Ottoman Empire. All of them were sunnis. So, it was never a war among denominations. It was a war for power. And I don't deny sectarians sometimes have been used by the greedy politicians. But, we need to see that different views among Islamic sects were never a reason for fight. You may not be knowledgeable about history of "Muslim" empires-dynasties etc. But, I am sure, as you gave a likeness as an example, you can relate to this through the history of conflicts among the Christian Europe.
The problem is politicians fueling and using sectarianism for their agenda. Even in Syria and Iraq, forgetting about the past few decades, if we study it, we can see that there was never a conflict between denominations. It is the politics that start it and I believe it is the same thing that could end it. If there were never an invasion in Iraq, a western support for "moderate" rebels in Syria (more than half of which joined ISIL), do you think such insurgents could create a conflict and destroy nations? I don't think so.
It is mainly wrong politics of global powers and their puppets in the region (such as Turkey, Qatar, etc) which have supported these extremists. And it is ironic, they claim they want to stop it now. Maybe they are worried such terrorist groups can't achieve their aim of toppling Syrian government, and they want to do it themselves. Who knows. After forming and using a group, then you make excuse of that group and invade nation. Wasn't it the American govt's politics for using Afghani seperatists and making them excuse invading and plundering nations? Same goes for Saddam. Same goes for "Syrian" rebels. Same will go for Kurdish "freedom" fighters.
As long as such imperial meddlings continue, and that there are regional puppets who support conflicts for American project of new Middle Eeast and North Africa -as they admit it themselves, like in the below video Erdogan admits- I'm sure it will take longer to end this bloodshed.
[youtube]pZyV9eFxMTI[/youtube]
AKP Recep Tayyip Erdo
But, when such global and regional monsters who create conflicts are stopped, I am sure the world will turn into a transient paradise.
In any case, the problem is not the differences of views in kalam (theology), history and fiqh (jurisprudence) among Muslim denominations, or Christian ones, or etc. And a fight over who is right. It is not so. It has never been so.
Once, people analyze current politics without getting into racism or sectarianism, they can realize the truth. And when you do that, it doesn't matter which denominational differences you and others have, vigilant Muslims won't fall to extremism and conflicts.
But, I agree, getting to know the beliefs and practices of each other is necessary, so that believers won't fall for propaganda of extremists. And sadly, there is a lot of misinformation/disinformation our there against Muslims, namely shia and sufi Muslims as they are minority which goes like; "The believe in such and such. They do such and such." Thus, a person needs to study a denominations with the subscribers of that denomination. S/He does not have to accept it, but at least s/he will know the truth and not believe in gossips. And, when you do that, it will not be an unknown to you any more. Thus, you won't be afraid of that. You won't take actions against that. And so on.
Sorry for rambling. And thanks again for your concern, prayers and well wishes.
I know I did not adress the question in the title, but I am sure brethren here will adress it. Also you might check related threads in Sunni DIR as well.
ma salam