GeoGraphics[Text[Style["Hello!", 150]], GeoRange -> World]
In any other language, if I wanted to write some text on a graphic, I would find a routine to load an image into memory and another to render text into that memory. That's genuinely easy.
But in Wolfram's case, I'm apparently just supposed to know that there's something called "GeoGraphics" that does this kind of thing, that the text goes in a Style[] block (what?), and "GeoRange -> World" is how you tell it to create a worldmap as a background. WTF. And don't tell me "read the docs", because even if I found this, it wouldn't help me much with the rest: