To provide proper healthcare to every child (and adult) on earth we'd need to stop the people who are currently limiting the availability of healthcare: the hospital cartels preventing the construction of new hospitals, the medical associations preventing the training of more doctors, the pharmaceutical companies preventing the free trade of medicines, and the governments colluding in all that.
But they'll fight that every step of the way and one of them most effective ways they fight it is by talking about money, as if lack of healthcare spending was the problem. It's not. We'd actually spend less on a more accessible healthcare system, because all the people sucking the money and life out of the current system wouldn't be getting richer.