The problem, when it comes down to it, is this:
the founding fathers decided America would be a place of freedom both of religion
as well as from religion
. Ergo church and state are seperated.
If you want to teach creation myth, then fine - but understand it isn't science and can't claim to be, neither can this broadside sneak-attack 'intelligent design'. In addition to that you have to give space to all of the various religions and creation myths, unless you want to declare America as only one faith.
If you want to turn the USA into a religious theocracy, start thinking about what happened the last time religion had that much power: salem witch-trials, the inquisition - and just incase you were wondering, a later example is afghanistan before y'all invaded