Charles himself will only have income from his estate (whereas his mother had income from the Civil List)
What I meant to say is that in the blink of an eye, realistically -- in a couple of generations -- you could and probably will have a situation where a single land-owning family in the USA could end up with a very similar proportion of a _vastly_ larger country.
It's probably in the nature of land-owning for this to happen: someone ends up with all of it, then can't maintain it, and it ends up being sold off or dispensed to the state, then sold off, reaccumulated, and the circle continues.
And I think it's a mistake to see the royal family's land ownership as a source of power and influence. Unfortunately we give them the power and influence for no really good reason; the land is a side thing.