The testing method aside. U.S. citizens general lack of understanding in technology should surprise no one. So many people in this millennial peer group don't know how to use the internet beyond popular websites, email, and smartphones with a few shortcuts thrown. Since making a deliberate effort to actually understand how a lot of technology works/things get made, I realize how absolutely ignorant we are, but feel really good about it. That's quintessential American. What I think a lot of this peer group does understand is how important the internet is in general, so we have that going for us.
Did you look at the sample questions? Familiarity with email, a first-grade proficiency with a smart phone and the ability to use a web browser ought to be more than enough. I read the results as indicating that most Americans don't have those skills. EDIT: if kb is to be believed, perhaps I'm wrong. Maybe the real test is different from the samples (though -- what's the point?).