Not much would change imo, alot of local issues would probably exist that don't relate to religion

We would have a smaller more sustainable society, that is more educated, and values life more. When you believe that the party does not start until you are dead, you end up with violent people believing that they just have to ask gods forgiveness, and they will end up with sky daddy in heaven.

Agnostic government won't happen without significant agnostic populace, so don't hold your breath. I imagine it would be a lot like Norway or the Netherlands, with a real environment protection policy, rapidly growing electric car and light rail infrastructure, smart electrical grid, universal healthcare, subsidized daycare, proper education, including subsidized college, low incarceration rates and an end to the death penalty, and on and on. But the fundies won't go quietly, that is for certain. ????

Be more reasonable ...

I think we would be living out among the stars in a few more years if that was the case. We would have an actual city on the moon, perhaps a colony or two on Mars and maybe even Europa. Better social conditions here on the planet and green energy would run almost everything.

I think it would be better, less tax breaks for churches etc would be more easily addressed, but politicians being what they are, I would not hope for much.

Equality!