The Nicene Creed, which is historically one of the most important trinitarian confessions, begins by saying “We believe in one God, the Father Almighty…”. Scripture speaks this way as well:
“This is eternal life, that they may know You, the only true God, and Jesus Christ whom You have sent.” John 17:3 NAS
“…yet for us there is but one God, the Father, from whom are all things and we exist for Him; and one Lord, Jesus Christ, by whom are all things, and we exist through Him.” 1 Corinthians 8:6 NAS
But the equation of the “one God” with the person of the Father in particular is something that many modern Christians are uncomfortable with. There are actually quite a few legitimate reasons why this might be the case.
Many anti-trinitarian heresies comandeer this sort of language to try to argue against the divinity of Christ. Jews, Arians, Unitarians, Socinians, Muslims, and various other anti-trinitarian heresies all argue that the one God is the Father in particular in order to exclude the Son from the divine nature, denying His divinity. They try to weaponize what the Nicene Creed lays out as the first article of the Christian faith, in order to deny the second.
In light of this, it is understandable that the language of “the one God being the Father” would make some people uncomfortable.
Despite this, I would argue that we must seek to reclaim the language of scripture on this matter, rather than cast it aside because if its misuse by heretics. Defining the “one God” of the Christian faith as the Father is something scripture does, and language scripture uses. Its the way that God chose to reveal these truths to us. We must seek to embrace the langauge scripture uses on this matter, while being careful at the same time to distinguish what we believe from anti-trinitarian heresies.
This is precisely what the early church did. Although in the first few centuries of Christianity the church was faced with several heresies attacking the fundamental articles of the faith, including the divinity of Christ, hereies which often twisted and misused scripture in doing so, the early church did not reject the concepts and language of scripture that were being misused. Rather, they contended for them, and carefully distinguished what they were saying from the false teaching of the various heretical sects. This is why the Nicene Council, for example, although writing in opposition to Arianism in the defense of trinitarianism, did not shy away from saying that the “one God” is “the Father Almighty” in the very document in which they were articulating the doctrine of the Trinity. Its misuse by heretics did not stop them from embracing the doctrine that the one God is the person of the Father- instead they sought to demonstrate how this truth is compatible with the other doctrines that scripture teaches that Arianism opposed, such as the divinity of the Son.