Re: Not a lot he can sue for
Freedom of Speech in the US means that the press/media can say anything they like.
That is wildly, fabulously wrong.
There are most certainly limitations on expression in the US, both expressly legislated and in practice. In the case of the "media" (which, for most purposes, has no special legal status here, as distinct from any other public expression), libel law attaches, as do various consumer protections that restrict forms of expression deemed dangerous, such as making certain kinds of claims about medical efficacy.
In order to claim damages he'd have to prove it was malicious or similar.
You do see this contradicts your first claim, right?
In the US, there are a variety of libel laws at the federal and state level, so to some extent it depends on in which jurisdiction Nakamoto files suit. In many cases the barrier for libel is high (and in general it's higher in the US than in most other countries, thank goodness), but Nakamoto is not a public figure, which helps.
Ordinarily, under US federal libel law, he'd have to demonstrate that Newsweek knew their statements were false, or they recklessly disregarded the possibility they were false; that the statements didn't constitute "opinion" or "fair comment" (seems a priori true, but IANAL); and that his character was impeached and his reputation damaged. I think he could make a decent case there, but I wouldn't want to bet on it.
He could also claim "defamation per se", which has weaker tests. The two possible categories that could apply there (in this case) are accusing someone of a crime, and interfering with their ability to conduct business. But creating Bitcoin probably wasn't a crime now, and even if cryptocurrencies are criminalized in the future, the prohibition on ex post facto criminalization means that doesn't apply. And from what I've read, I think he'd have a hard time making the case that Newsweek has interfered with his ability to make a living.