It is equally challenging as both of those examples, but it's very very important so it's worth working on despite the intractability.
In terms of alignment among humans, most (but not all) human governments agree on certain principles, which are encoded in international law and negotiated within the United Nations.
E.g., most (not all) people agree that torture and slavery are unacceptable.
Thus, it is possible and important to get AGI to abide by these high-level human values. E.g. if an AGI system is put in charge of maximizing the GDP of a nation, it should do so in accordance with generally recognized principles of human rights and human dignity.
There's certainly a lack of agreement among nations but at least we mostly agree on some things and getting AI to agree with us on the things we agree on is important.
If you like podcasts, here's a great podcast episode which explores a philosopher's perspective on how to make moral decisions (e.g. should abortion be legal) in a situation of moral uncertainty:
https://futureoflife.org/2018/09/17/moral-uncertainty-and-th...
