My mother wants to donate $100,000 to a school in Lithuania. How do we set her up to be a charity so she can write it off?
As you suggest, a U.S. taxpayer is unable to take a charitable contribution deduction for a gift to a foreign charity. (I am assuming that the Lithuanian school would qualify as a public charity here.) A U.S. charity could make a gift abroad, but it would be expensive and tedious to establish a U.S. charity solely to make a single gift. The charity would be a private foundation if it did not receive sufficient public support from others and would require even more paperwork in order to make the gift.
Your best bet would probably be to find a community foundation, a “commercial” donor advised fund organization, or some other U.S. public charity that is willing to take contributions from U.S. citizens and then re-grant the funds abroad. You could not “earmark” the gift, and the U.S. charity would have to maintain discretion and control, but you can probably find organizations that will be willing to work with you on the situation.