Religion is a sort of limited choice. Spirituality is almost completely individual - each person develops their own idea/relationship with existential purpose and what it is the experience of life amounts to.
Religion is an institution of a culture's spirituality. There are a limited number of these to identify with, and many of them we are affiliated with long before we begin to develop our individual spiritual understandings. Most people stay within their cultural spiritual identity - their religion. Their individual beliefs will vary, but you don't see a whole lot of Baptists in the middle of America becoming Buddhists. Most of them will simply become 'non-practicing' or 'Christmas Christians' who show up on Christmas and Easter, then never really look back. They MAY get a wild hair up their ass and change denominations to Methodist, or something, because one church has better music in their service or their wife is more of the church goer than they are, and so she gets the pick of what church everyone is going to. There are the exotic religions to be found in the city, and it gets announced that so-and-so a church is hosting some cross-faith service or something, so the whole town piles in to figure out what is going on with the space alien.
It's much the same way in the rest of the world. Only in areas where you have major converging religions do you really see much thought put into religion. Even then, religion mostly takes on a political aspect. Families become more careful to ensure a competing religion isn't given dominance over their descendants, people pay more attention to what faith the governor is, etc. Conversions are largely political and for optics, at least in the public sphere.
So, in this sense, religion is a bit of a choice, but most people have little reason to engage with that choice. Even then, sweeping personal understandings can occur with regard to spirituality, and a person still not change their religion. One of my friends is not necessarily an atheist, per se - but he sees the benefits of religion, prayer, etc as effectively a sort of placebo for people to motivate themselves beyond fear or doubt. Since people over-estimate risk, we often have a much higher odds of succeeding than we feel we do - that prayer is the little bit of nudge to get us to commit to taking a risk we think is far riskier than it is - and we succeed, praise be! He sees the value it brings to the community to have a rallying tool, and sees it as being well worth participating in, even if he has no real opinion on the after-life.
For me, oddly enough, I believe greatly in a spiritual component that goes beyond the physical description of our world. But, that's another story that goes way further than we need to. You could find both of us in the same church and discussing many of the same pieces of scripture, finding many of the same points of value or critique.
