100% agree, but it's worth noting that US entities/individuals don't get a tax deduction for donating to a non-US registered non-profit without going through a (super complicated) intermediary like a donor-advised fund.
Only the entities and individuals based on the country where the foundation is located are going to benefit from the potentially simpler procedures of donating to a local foundation.
Finding "the best" country to register a Rust "thing" (foundation, NGO, etc.) is probably a very complicated financial and legal engineering problem that will need to balance a lot of trade-offs.
For example, ISO is not a foundation, but an NGO based in Switzerland. And the "Standard C++ foundation" is a 501(c)(6) based in Washington. We should probably seek legal and financial advise from experts here.
@nikomatsakis Would it make more sense for the current Rust sponsors donating CI time, etc. to donate this services (instead of money) to the Rust foundation directly ? AFAIK companies can donate pretty much anything, not only money, e.g., some book editors have donated the copyright and material of some of their C++ books to the Standard C++ foundation, allowing it to provide these materials online for free.
I don't know if it might be more beneficial from a tax perspective for companies to have developers working on Rust by donating them to a Rust foundation.