The impression I'm getting here is that the teacher was over-using God with relation to the declaration. I seem to recall that America's founding father were not deeply religious people (in fact, if they were Irish, English and Spanish, we are talking Protestants, Catholics and CofE, it's like putting 3 cats in the same plastic bag, it just results in lots of hissing, claws and fur).
The teacher, however, seemsed to be trying to imply that America had been a 'Holy mission' from the start, to create a country founded on the laws of Christianity, which wasn't the case.
If that is the case, then the teacher is not giving their pupiils an unbiased view, which is not how you teach.