Well, it's certainly not safe for them to continue running under the .it TLD if they're in violation of Italian law, but they could redirect to "it.wikipedia.co

Well, it's certainly not safe for them to continue running under the .it TLD if they're in violation of Italian law, but they could redirect to "it.wikipedia.com" (which, I just checked, actually is the Italian Wikipedia) and thus be within the US domainspace. That seems pretty safe. And yes, you're correct that the US has asserted control over the generic .com/.org TLDs for historical reasons. They have a "silent .us" appended to them, from a functional standpoint. So they're not safe if you're in violation of US laws, but that doesn't seem to be the situation here.