Shamanism is not a religion, nor do you need to have specific religious beliefs for shamanic work to help you. I have had clients who are devout Christians, middle-of-the-road Christians, Islamists, Jewish, Buddhists, atheists, Native American religious practitioners, New Age followers, pagans--all helped with shamanic work. I have had clients who don't even believe that shamanism works, yet who walk out of a session believers in it and profoundly changed by their experience.
All cultures have produced their own shamans, though they might be called by other names: wise women, conjure women, curanderos, chamans, "witch doctors" (not a native term), medicine men and women, etc. In the western cultures, the shamanic tradition died out for a time, though there is a modern resurgence with "Neo-Shamanism." Today there is a rebirth of shamanism around the globe, but especially in the western cultures. It spans voids left out of modern medicine and psychiatry. Shamanism works and it helps people.