They surely are not part of Abraham's crowd of nations but I imagine that some of them believe in mono-theism.

Monotheism would be the rare exception, but it's not exclusive to religions descended from Judaism. Many forms of paganism have a one god / many names concept that is essentially monotheism.

And yes, you are right that I was looking for a common thread that the three religions have. To be honest, I am shocked at how many things these religions have in common. These commonalities tend to increase my faith in religion. Is that common?

I don't see why you would find it at all shocking. Islam builds on Christianity which builds on Judaism. It's perfectly natural that they share a lot in common.

I suspect you may be over impressed by how much they have in common because you have the common Christian misconception of Christianity as being a uniquely different religion. In fact, when Christianity was first being spread among the Romans one of the commonest complaints was that it plagiarized other older religions.

Jay