the minority of vocal founding fathers were deists. agnosticism is vastly different from deism.
you'll remember the colonies were the only place besides Belgium that Europeans could escape to, to practice their protestant religions, and Belguim was bloody expensive to live in. so the colonies were the only option.
the point of all the deist writings of the founding fathers was they didn't want us fucking up and doing the same shit Europe was doing. acknowledge a supreme deity and enumerate our rights and make it known that government had no business interfering/assisting/etc religion in any matter, and that government would respect the rights of religion to operate as it please so long as it doesn't interfere with anyone else's rights or property
if we had any balzz right now. someone sane would be on TV saying how the government has no right in interfering with the mosque being built near the WTC plaza, and that if there is some issue with "cultural history" of the building currently on the site its up to the citizens who purport it to be relevant to "cultural history" to place an offer to buy on the physical building and move it to another site.