...
Also, crime has been on a steady decline in the First World for more than a century...
Depends on where you are looking at, and the exact timelines(century is quite a big timeline). Small ups and downs are always there, still in quite a big part of the USA crime is pretty constantly on the rise and as mentioned before largly because of the criminalization of substance abuse. Looking at other "first world" countries you are right though, there is a relation between living in a wealthy country, wich has the means to help those of their population in need and crime rates.
Including my own opinion, social and liberal policies formost lead to these improvments, Whereby conservative right wing policies are mostly there to safe their own skins.
The curious thing about this simplification of religion and state in this context is:
Religion is claimed mostly by right wing, conservatives, traditionalist parties all over the world, while the messages within those religions often are better represented by the policies of social and liberal parties. That i see as quite a contradiction and again reason to leave religion out of politics.
sitenote:
Btw i dislike these categorizations making a difference in first/second/third world, whereby second world often isn't even used at all as term, just a difference between first and third world ^^ ... this i would see as condescending if i would live in a "third world" country categorized that way. When we are talking about countries with less GDP, then we could say countries with GDP lower then averrage or something similar, yes it is longer but also less arrogant.
Hopefully i can remind myself of that ^^, next time not to compare on a meta level/categorization but closer to the points to be done. Language matters.