Maybe it's time to declare war on the countries harboring and funding these organizations instead of making 'peace' deals with them.
Unfortunately it is not that simple. I believe that out of all the states in that region Saudi Arabia is the most likely candidate for being the source of funds. Reasons why I suspect that:
1. Their interpretation of Islam is quite strict and extreme: Wahhabism
2. They are by order of magnitude the richest in the region.
3. They have a history of supporting extremist groups in the past: wikipedia
However, US and Saudi Arabia are VERY close allies ever since World War 2: wikipedia.
According to the above link Saudi Arabia had supported 9/11 attacks. Osama was Saudi Arabian. 15 of the 19 hijackers were Saudi nationals and US were prevented from any investigation into them. One of the stated reasons behind the attack was the presence of US troops in Saudi Arabia and at the time of the attack it was reported that 95% of the surveyed Saudis supported bin Laden's cause.
Yet, despite all that, there was no action or reprimand by the US against Saudi Arabia. None. Afghanistan got invaded instead. I can't find a link, but I remember hearing that some families of the victims of 9/11 tried to sue Saudi Arabian government, but were barred due to diplomatic immunity. The US withdrawn the troops stationed there in 2003, thus bowing to one of the stated Osama's demands.
Given such extremely close ties, chances are slim that US will do anything if it is ever confirmed that Saudi Arabia is a financial source for Daesh. Perhaps Russia or France will.
I am very curious what US would do if Russia will launch strikes/declares war on Saudi Arabia...