• Community (friends, support group)
• Guidelines for morality / how to live life
• Shared stories / beliefs about the origin of their people
• Optimism and comfort from a belief in afterlife
• Charitable causes
In a way, I think religion has become "unbundled" over time, and these individual needs are increasingly being met my different alternatives (for example, meetups for meeting people, charities for helping others). But, of course, Americans are also just increasingly skeptical of religious beliefs.