The fact that a correlation between religion and fertility rates is completely bollocks (with the notable exceptions of some extremist/fundamentalist sects of Christianity such as Quiverfull and Amish as well as fringes of the Jewish Ultra-Orthodox movement). High reproduction rates are closely linked to poverty [1], and once wealth rises in a country or people migrate from poor/high-rate countries, birth rates drop accordingly [2].
Additionally, it's a simple numbers game. The US only has 1% of Muslim faith [3], the European continent has ~7.5% [4] Muslims (of which 2/3rds belong to Russia and Turkey - the European Union figure is ~3.3%), even India barely has 13% [5]. It's mathematically impossible for Islam to achieve dominance in any country it doesn't already have by population in any feasible time scale, especially as religious affiliation in general keeps dropping and dropping associated again with wealth and education levels.
In general, the "the Muslims will replace us demographically!!!" take is dominantly found on the far-right end of the political spectrum, with the worst of the worst being the virulently anti-semitic "great replacement" theory that alleges that a "new world order" led by Jews wants to "replace" the intelligent White Christian population with dumb Muslims [6]. Please, don't fall for that kind of baseless, vile propaganda.
[1]: https://www.theguardian.com/global-development/2016/aug/25/h...
[2]: https://www.knomad.org/sites/default/files/2020-01/Migration...
[3]: https://www.pewforum.org/2021/01/14/measuring-religion-in-pe...
[4]: https://de.wikipedia.org/wiki/Islam_in_Europa#Statistik
[5]: https://www.bpb.de/internationales/asien/indien/44418/muslim...
[6]: https://www.adl.org/resources/backgrounders/the-great-replac...