Aggregately, church enrollment is declining. It is declining relatively quickly in more "liberal" protestant churches and only marginally in more evangelical ones. In addition, there are clearly individual churches that are bucking the trend. I am unclear where the Catholic church stands since it is being aided by immigration and suffering due to the many scandals that have surfaced in recent years.

But I think "institutional" affiliation is declining in general. At the political level, more people identify as independent than Republican or Democrat. At the service organization, membership in many service clubs like Rotary and Kiwanis is declining. So, much the decline in church affiliation is likewise declining.

On the other hand, as society becomes more diverse and fractured, people are "joining" small groups some religious some not.

The religious ones have weekly Bible studies and get together to worship, read scripture, and pray. But they also gather to eat, share company, the bond.

It is hard to really measure where people are spiritually given these trends. But I think your question was towards "church" affiliation especially non-Catholic Christian church affiliation and while evangelical churches collectively are losing membership at much slower rates, I think many demographic factors are driving down membership across the board.