It would be nice if it were that simple, but it isn't. Maybe it would help to clarify the connection between Yoga and Buddhism. I use Buddhism because I know a little about it, and I don't know much about Hinduism. You have to think in terms of both philosophy and practice.
Buddhists actually incorporate some yoga practices as part of their religious practice. But yoga was practiced long before Buddha arrived on the scene, was developed independently and to this day is practiced independent of any connection to Buddhism.
In terms of philosophy, Yoga philosophy stands completely on its own, and is not specifically Buddhist or Hindu or anything other than Yoga philosophy. But all Indian philosophies, including Buddhism, were developed during the same time period and contain many similar ideas. That doesn't necessarily mean that these ideas conflict with Christianity. In fact learning about some of these concepts can often deepen one's understanding of his/her own faith. The concepts of karma and reincarnation, which are central to yoga philosophy, come to mind.
Yoga philosophy does contain a concept of a God or Isvara (the Lord), and of devotion to the Lord or religious practice. For adherents to particular religions, the question becomes, does Isvara represent a specific God that is peculiar to Yoga, or is Isvara an archetype that can be applied universally to any religion. The safe solution is to treat Isvara as an archetype, but in my opinion, Isvara does represent a specific God. The Samkhya-Yoga philosophy includes many very specific ideas about the nature of Isvara, some similar to Christianity and some different. Significantly, Isvara is a single God, which is very different from the many gods and goddesses found in Vedic literature. In my opinion, the concept of Isvara is very similar to the Christian concept of the Father. If there is only one God, then they must be the same.
As I said before, yoga can be practiced purely for its health benefits, which does not require one to accept or reject any philosophy or belief. Even at this most basic level, however, one is not likely to succeed in yoga without following basic rules of personal conduct and ethical behavior found in the Yoga Sutras. These are completely in line with Christian beliefs. In yoga philosophy they are considered universal principles, as opposed to the commandments of God. But what is a commandment of God if not a universal principle? Part of this set of principles is devotion to Isvara, but Yoga philosophy doesn't describe any devotional practices other than the repetition of the syllable OM. Most people would probably agree that following one's own religious beliefs and practices satisfies this principle. The Yoga Sutras does include a reference to deity practices, but I don't know anyone who does deity practices outside the context of Vajrayana Buddhism. And I can tell you that in Vajrayana practice, deities are not considered externally existent entities, they are considered to be mental constructs.
In my opinion, other yoga practices, especially meditation practices, are best understood in the context of yoga philosophy and Vedic spiritual practice. For those who have an open mind, these can be rewarding. Yoga is not dogmatic, and personal experience is key. One is encouraged to reject ideas, beliefs, or practices that are found to be false or do not conform with reason or personal experience.