My recollection of the "Born on the Bayou (CCR)" lyrics is that the word is Voodoo, which is a Haitian/Cajun southern and swampy word for evil magic. Voodoo has many pronunciations and spellings including hoodoo.

Hoodoo is a geologic term for the rock stacks, as seen in this picture, in the US desert southwest.

Really depends on the area! Some places in utah have 10 or so really magnificent ones, Bryce canyon has tens of thousands all clustered together in spines from the canyon rim. This area had the most I've ever seen that are all free standing on their own and not connected. They ranged in size from hundreds of feet high, to a few inches.

I think in that case they are referring hoodoo in the context of: https://en.m.wikipedia.org/wiki/Hoodoo_(spirituality)

Southern Louisiana native here, hoodoo generally refers to the supernaturalism of African Americans found along the Mississippi, not to be confused with voodoo which is just veiled west African ancestor worship

Western North America has them in a few areas, usually in arid or semi-arid locations. They are formed by the wind and water erosion of sedimentary rock.

Bryce Canyon National Park in Utah and Chiricahua National Monument in Arizona are the two main areas to see hoodoos in the states. I highly recommend visiting Chiricahua before it becomes a National Park. Lots of great wine in that area too.