we're not the only or even the main cause.
Actually if we just take the three examples given in the OP and look at the historical incidents that have led to the current situation in those countries I would say Western countries have played a major part in causing the problems there some of them deliberately created by colonial policies of European countries. With Gaza and Iraq its fairly well known how the British and Americans played a big role in the situation there but the role the French played in bringing the minority Alawites to dominance in Syria is less known.
'When the French began to occupy Syria in 1920,[30] an Alawite State was created in the coastal and mountain country comprising most Alawite villages; the French justified this by citing differences between the "backwards" mountain people and the mainstream Sunnis. The division also intended to protect the Alawite people from more-powerful majorities, such as the Sunnis.
The French also created microstates, such as Greater Lebanon for the Maronite Christians and Jabal al-Druze for the Druze. Aleppo and Damascus were also separate states.[31] Under the Mandate many Alawite chieftains supported a separate Alawite nation, and tried to convert their autonomy into independence.
The French encouraged Alawites to join their military forces, in part to provide a counterweight to the Sunni majority (which was more hostile to their rule). According to a 1935 letter by the French minister of war, the French considered the Alawites and the Druze the only "warlike races" in the Mandate territories.[32]'
Basically the French sowed the seeds of the sectarian strife we are currently seeing now in Syria. You know the saying 'divide and conquer'.
Also looking at the three countries history they have not been blighted with bloodshed throughout and have had periods of turmoil and periods of peace and prosperity just like any other other part of the world so your assertion that they would be 'killing each other anyway' as if they are some sort of sub-human savages that enjoy war is just a load of rubbish.
As for your comment about Western interference in the region the problem is we are not honest brokers. We talk about human rights violations in one place and then ignore the abuses of our allies. We talk about lack of democracy across the middle east but then prop up dictators. We start wars because of supposed violations of UN resolutions an then actively ignore or veto actions to deal with violations of UN resolutions by Isrealis. No we cant solve the problems of the region but we can certainly stop making them worse with our ruthless pursuit of our own economic interests regardless of the consequences an human costs to people living in those countries.