Is it more difficult to score a Tenure Track position in the US when applying from outside? I am currently located in central Europe. When I was hunting for an assistant professor position some months ago, I was also planning to apply to some US institutions for Tenure Track positions. However, one senior professor with some experience working in the US told me pretty much straight-up that this will be a waste of time, as "US universities do not hire people from outside the US/Canada on Tenure Tracks". Relativizing somewhat, stated that "of course exceptions exist, especially if they personally know the applicant, but generally you will get onto the reject pile immediately as they don't know your school well enough.". I was counselled to apply for a postdoc at an US institution first, if I really wanted to get into an US school.

Looking over the CVs of some existing assistant professors in good schools the statement could  be accurate (almost nobody with the job title Assistant Professor seems to come directly from outside the US - many graduated somewhere else, but the last position before was almost always an US institution).

In your experience, is this sentiment correct? Does it even make sense to apply for a TT position in the US from outside (under the assumption that your CV is reasonable for a TT in the first place, of course)? Computer Science is most relevant to me, but any information from any STEM fields would be interesting as well.
While the "I don't know your university" element can have an influence on whether your application gets summarily dismissed to the reject pile, it's less of an issue than one might think. We all travel to Europe and Asia for conferences now, and meet colleagues who come from different countries. I can probably name the top few universities in my field in many European countries, as well as personally know people in each of them. 

But there's a more mundane logistical reason for potentially avoiding applicants from other countries: expenses. There's always a risk in getting someone to come for an on-site interview, but with a foreign candidate the expense and logistical work (visa processing, payment methods and so on) are more onerous. We always want to find strong candidates, but when there's a large pool of highly qualified candidates in the US, it can be convenient to focus on those that we expect have a chance of actually making it through the interview process and coming. 

There's also the question of whether someone from Europe (as opposed to someone working there) really does want to come to the US, or is just casting a wide net. But that can be addressed in candidate statements or even conversations. 

None of this means that foreign candidates are disqualified. Far from it. But it creates a moment of doubt.