A lot will depend on how one defines the terms you're using here, but, broadly speaking, it is certainly true that European and American enslavers encouraged, and often forced, the enslaved people they controlled to convert from African religions to Christianity. There were specific reasons for this that went well beyond their general belief that Christianity was the "true" religion and was characteristic of "civilisation". Among the most important of these was that the Bible contains a number of passages that mandate loyalty and devotion to "masters" (meaning originally a master-servant relationship, not an enslaver-enslaved relationship), and warn of the awful spiritual consequences that disloyal or rebellious servants face. These could be used in an attempt to control the behaviour of the enslaved.

Harriet Jacobs, who escaped from enslavement in the south and published her recollections of the slave system in her Incidents in the Life of a Slave Girl in New York in 1861, offers a – sarcastic – account of how Christianity was used in this context, specifically in the aftermath of the Nat Turner rebellion of 1831, which resulted in the deaths of about 60 white people in the district in which Turner had been enslaved. It's worth noting, in this context, that (as I pointed out in an earlier response) this rebellion had itself been inspired by Turner's apocalyptic reading of some Biblical texts.

After the alarm caused by Nat Turner's rebellion had subsided, the slaveholders came to the conclusion that it would be well to give the slaves enough of religious instruction to keep them from murdering their masters. The Episcopal clergyman offered to hold a separate service on Sundays for their benefit...

The Reverend Mr. Pike gave out the texts he wished the slaves to repeat or respond to.

His text was, "Servants, be obedient to them that are your masters, with fear and trembling, as unto Christ."

Pious Mr. Pike brushed up his hair till it stood upright, and, in deep, solemn tones, began: "Hearken, you servants! Give strict heed unto my words. You are rebellious sinners. Instead of serving your masters faithfully, which is pleasing in the sight of your heavenly Master, you are idle, and shirk your work. Instead of being engaged in worshipping him, you are hidden away somewhere, feasting on your masters’ substance; tossing coffee-grounds with some wicked fortune-teller, or tying up little bags of roots to bury under the door-steps to poison each other with.

“If you disobey your earthly master, you offend your heavenly Master."

The second key reason why enslavers feared African religion was that it provided a psychological outlet for the enslaved that encouraged them to believe they had agency and could draw on powers much greater than they possessed alone – in short, it encouraged resistance. Perhaps the best known example of this occurred in Haiti in the immediate run-up to the successful rebellion that began there in 1791 and which, as you probably know, remains in fact the only ultimately successful example of a rebellion by the enslaved people of the New World against their enslavers. Historians of Haiti generally accept that this rebellion began with a religious meeting known as the Bois Caiman ceremony, which was apparently organised by practitioners of Vodou. Wade Davies has argued that Vodou/Vodoun is a "quintessentially democratic faith" and as such a potentially liberating force that is explicitly opposed to any "repressive social order". It certainly acted as a reminder of the origins of the enslaved people who practised it, and of the fact that they had once been free, potentially encouraging a sense of national identity and solidarity among the Haitian rebels. Carolyn Flick puts it this way (using the older spelling of the term):

Despite rigid prohibitions, voodoo was indeed one of the few areas of totally autonomous activity for African slaves. As a religion and a vital spiritual force, it was a source of psychological liberation in that it enabled them to express and reaffirm that self-existence they objectively recognised through their own labour... Voodoo further enabled the slaves to break away psychologically from the very real and concrete chains of slavery and to see themselves as independent beings; in short, it gave them a sense of human dignity and enabled them to survive... The sheer tenacity and vigorous with which slaves worshipped their gods and danced in their honor... eloquently attest to voodoo as a driving force of resistance in the daily lives of slaves.

It was for this reason that the French law code imposed on the sugar islands they controlled – the so-called Code Noir – explicitly mandated conversion to Christianity for all newly-arrived enslaved people. The code was written in the voice of the King of France, and this injunction was considered important enough to place first in what was a fairly long and complex document. Breaches of these two clauses were also, it's very interesting to note, the only ones in the entire code which might potentially result in the enslavers themselves suffering the death penalty for treason:

I. All the slaves who will be in our islands will be baptised and instructed in the Catholic religion. Those who will buy newly arrived slaves must inform the Governor of the said islands within a week or face a discretionary fine. Our officials will give the necessary orders to have them instructed and baptised.

II. We forbid any public exercise of any religion other than the Catholic faith; we wish that offenders be punished as rebels against the French state. We prohibit all secret religious meetings, which we declare treason, and masters who allow or tolerate such meetings among their slaves will be subject to the same penalties.

Sources

Wade Davies, "The ethnosphere and the academy" (2014)

Carolyn Flick, The Making of Haiti: the Saint-Domingue Revolution from Below (Knoxville, 1990)

Harriet Jacobs, Incidents in the Life of a Slave Girl, Told By Herself (New York, 1861)