I'm the first one to be suspicious of these man on the street videos. And yet, why should I be surprised at the results? One commenter mentions a Huffington Post story about respondents at a university not knowing that George Washington was the general at Yorktown. Why would they? My boys' history texts in high school didn't mention it. Unless the teacher pointed it out, it wasn't there.
Likewise, my boys' American History textbook in sixth grade barely mentioned the Declaration of Independence. It had two pages devoted to the Declaration. The first couple of paragraphs of the first page mentioned the Founders wanting a justification for revolution and a couple tidbits about the writing of it and a couple quotes. But that was it. 60% of the rest was spent focusing on the fact that we shafted the Native Americans, we owned slaves and women couldn't vote (I found it interesting that it didn't mention that white men couldn't vote either, unless certain conditions were met). The second of the two pages was a giant Civil Rights History poster featuring Martin Luther King, Jr.
So if you asked them things about the Declaration of Independence or who was at Yorktown, exactly why would you expect them to know anything? We're not teaching these things. We're teaching liberal indoctrination 101. That's what our schools teach. That's what our textbooks teach (BTW, I worked for a few months, and my wife worked for several years, in a textbook publishing company), and it's what our institutions of higher learning teach. Perhaps some teachers and professors buck the system, but they are the exceptions.
These questions all ask things that would have been known from schoolbooks and classrooms about 20 or 30 years ago. Not today. Kids growing up today know little about our country, our history, or much of anything in the humanities. Most lessons focus on the bad of our history, with the sidebars being the main points of celebration. Supplemental materials are almost exclusively focused on a liberal perspective, such as America as a genocidal nation of slave owners, America as an Imperial power, religious intolerance and secular enlightenment in Europe (all of these are handouts my boys received).
So let's not assume these man on the street interviews are not without some level of editing for impact. But let's not be shocked that people under about 40 years old wouldn't know questions that would have been known decades ago. Unless they went looking for themselves, they probably never heard of such things.