That is a naive thinking. If US has a defense system against nuclear weapons but you can attack it via social media the error is on the US side. US is not an exception and had also attacked a lot of countries before via different strategies.
Uh okay, but that doesn't mean the US shouldn't examine this and respond as necessary.
Sure, I am just saying that it is "funny" that a superpower is attacked via social media in a naive way. This attack could be organized by any other entity with enough cash. It sounds like an easy hack.