What are some essay ideas for eliminating religion from marriages?

I'm writing an essay in my Writing 122 course arguing that religion should be removed from marriages in the US because it would decrease divorce rates and (for once) completely separate church and state in that aspect. Are there any suggested sources I should use to find some solid statistical evidence? Does anyone have any counterarguments I need to address? Are there any other ideas for improving my argument and making it more supported? Anything is helpful...thanks.