I live in the UK and have yet to hear anyone prattling about "manifesting" in everyday life, but I do see it all the time online, and it is irksome for all the reasons you describe.

I'm a Christian of fairly orthodox theology (though I don't call myself "evangelical" as that seems to translate as "right-wing lunatic" these days rather than someone who believes in preaching the Gospel). I see the idea of "manifesting" as a perversion of having faith in God. Faith is not a magic spell for selfish gain, but as a Christian, one has to have faith for what one believes God has promised.

For example, I have faith that sick people for whom I'm praying will be healed, or that those troubled (by all sorts of things) will find comfort and peace. According to the Bible, in James chapter 1 verse 27, the kind of religion God accepts is to look after widows and orphans, and to ensure one is not corrupted by the world. Knowing that is God's will, one has faith amid those parameters, hoping to see God's power manifest for good.

This is fundamentally different to the kind of selfish, narcissistic "manifesting" to which you refer here.