There are no US laws that require that aid be given to any country.
As another poster has pointed out, this is not actually true. Congress decides these things and its decisions are law.
USAID has been a total cash sink, as DOGE exposed, and Rubio did the right thing by winding it up and incorporating it into the State Department
Ugh. This reminds me of various executives at various companies who are always naming departments in sectors like IT, R&D, Customer support, security, or really just non-sales payroll in general (because these guys almost always seem to come out of sales or finance) are just leeches to them.
Understanding why USAID is not a total cash sink involves a two pronged perspective. Some people agree with one prong, others agree with the other prong, and a lot of people agree with both, because they are not mutually exclusive. The prongs are aligned with an axis. At one extreme end of this axis is soulless ghouls sitting on a pile of money and children's skulls and jealously guarding it. The children's skulls are there for convenience as containers for some of the money since they are cheap and disposable. From their view, nothing matters but the accumulation of wealth, and suffering is irrelevant or even desirable, because it means that other people are losing, and therefore the ghoul is winning by comparison. At the other end of the spectrum are summer children with flowers in their hair who dance and sing and weep for any hint of sadness in the world. Their hearts bleed for the merest hint of suffering of the smallest of living things. Heck, their hearts weep for the imagined suffering of inanimate objects. Somewhere in the middle is where you find most people. Certainly leaning to one side or the other. The point is that one prong of the argument for organizations like USAID is that if we can reduce human suffering by spending so relatively little, we have a moral obligation to.
I think that prong is the one you're thinking of, and it disgusts you. All those flower children who are simultaneously sappy bleeding heart simps and also blood sucking monsters stealing from you and sapping and impurifying your precious bodily fluids. You're ignoring the other prong though. That prong is that organizations like USAID have always been an important part of US soft power. They are the sort of thing that, when people criticize the US about all the crappy things it absolutely does, they can look at things like USAID and say "yes, but...". So many people can be helped with so little. Many of them have their lives saved by the aid and many of them aren't blind to the US flags on those packages of food or on the medical supplies, etc. Time passes, and they live their lives and, whether it's considered a debt, or gratitude, or a simple positive mental association, someday the US needs some good will in an area and some people say "we must oppose the the US imperialist swine!" or something to that effect, but some of the people remember that aid and say: "yes, but...".
So, consider it an advertising budget, or a bribe, or whatever you want but, even if your attitude is soulless pragmatism, there's a soulless, pragmatic reason for it too. It sits there right alongside the sappy, bleeding heart reason