What are some major ways that American religion in the late 20th/early 21st century has evolved? Explain why spirituality has emerged as a popular choice of belief and practice for Americans. How do you see this being expressed in our social behavior and in our political development?

A Pew Research Center study on spirituality from 2015 (see the link below) found that fewer Americans are affiliated with established religious groups than in the past. More Americans than ever before are not associated with any religious group, and this is true across racial, ethnic, and socio-economic lines. In addition, the percentage of Americans identifying as Christian is declining (though the number of evangelical Protestants has remained roughly the same). In addition, while still small, the numbers of non-Christians (including Hindus, Muslims, Buddhists, and Jews) are growing. 
Spirituality is a way for the growing number of Americans who do not associate with a specific religion to still feel a sense of the divine. It has infused our culture through practices such as mindfulness and meditation, and it has resulted in people seeking a sense of the divine outside of mainstream religious practice and worship. In addition, it has become less important for political figures to profess a sense of religiosity or to claim ties to an established form of worship (though evangelical voters still find these types of ties important).  
https://www.pewforum.org/2015/05/12/americas-changing-religious-landscape/