As intrinsically social animals, we have general obligations toward other people that precede our consent. How these play out in practice will be determined by the limitations and conditions of the situation. But in general, such obligations radiate outward based on proximity of relation.
Our first obligations are toward our immediate families. As the human race is essentially a large extended family, the obligations dissipate the further out we go. We do have a general obligation to help those in need, but this obligation is prioritized. In classical texts, this is called the ordo amoris or "order of love" (in the older, more technically accurate terminology, order of charity, where "charity" - from caritas - means willing the good of the other).
Now, to address your comment specifically...
> There's already a lot that the US taxpayer is on the hook for that's a lot less valuable than a best on the next big thing in software, productivity, and warfare.
For example? Whatever the benefits of LLMs, I find this relative exuberance unreasonable.
> It shouldn't be the job of the US taxpayer to feed someone that doesn't want to work,
In someone able-bodied and of sound mind refuses to work, then we don't have an obligation to support someone like that. This is true. In fact, it would be uncharitable to enable their laziness, because it harms the character and virtue of that person. Of course, in practice, if someone you have determined is able to work is found starving and in danger of death, for example, then it is unlikely they are merely lazy. Would a man of sound mind allow himself to starve?
The manner in which we deal with such cases is a prudential matter, not a matter or principle. We need to determine how best to satisfy the principle in the given circumstances, and there is room for debate here.
> it absolutely shouldn't be the job of the US taxpayer to feed another country's citizens half a world away.
If there is a humanitarian crisis somewhere in the world, for example, then there is a general obligation of the entire world to help those affected. How that happens, how that is coordinate, is a matter of prudence and implementation detail, as it were. Naturally, several factors enter the equation (proximity, wealth, etc).