They want someone else to take responsibility,not because of the horrific violence they know will be required to decisively defeat their enemy.
Violence on a barbaric scale after all is second nature to Islam,but they don't want this violence to be inflicted upon them.

Better to let big ,goofy USA to do their dirty work, take the risks, loss of lives and immense costs.

The Gulf War of 1990 was typical,where the Saudis successfully requested US military assistance against the Iraqis because of their invasion of Kuwait.

The Saudis in particular have a lot to answer for.
The Saudi financed Madrasas religious schools are worldwide.

They are a hotbed of fundamental Salafist teachings and cancerous breeding grounds for terrorism against the West.

This quandary is unresolved.

These Madrasas activities,plus the unofficial seeming reluctance to stop the financing of terrorism, are carried out in full view of the world,but at the same time they manage to profess friendship with the U.S. and they get away with it.

The Americans are waiting for the day when their new found oil and gas resources will allow them to get tough with the Saudis.