I have made numerous bows with Black Walnut and combinations with other woods and Bamboo It's a classic American wood, easy to come by and relatively inexpensive. No failures, so far!
I have also used soft Maple, Birch, Alder, Butternut, Ornamental Juniper, Sweetgum, etc.....
I have a friend who is an Arborist and gifts me random chunks of wood.