Oh say can you see?

There's a group going around the country teaching people the lyrics to "The Star-Spangled Banner"; they're visiting St Louis today. They claim 2 of 3 Americans don't know the words. I want to know where they are finding these people. Are they counting children and brand-new immigrants who wouldn't have had a chance to learn them yet? Or are they counting people who only know the first verse as "not knowing" the words? I'm boggled. I can't imagine growing up in the US and not knowing them (well, the first verse anyhow). So. A poll.

[Poll #672326]

I'm curious, also, whether non-USians "typically" know the words to their own national anthems, and how that might differ by country of origin. Please feel free to answer in comments.