It's a play on titles from self help programs which utilize ellipsis.
For example I lost 20 pounds in 4 days, and so can you.
This is a kind of strange ellipsis, because just tacking on "[lose 20 pounds in 4 days]" doesn't really create a grammatical sentence, but it's something like that.
The ellipsis would be clearer if the sentences were I lost 20 pounds in 4 days, and you can [lose 20 pounds in 4 days] too.
I am America, and you can [be America] too.
And the ellipsis is not so great with "to be", either.
Here's some discussion from Language Log: http://itre.cis.upenn.edu/~myl/languagelog/archives/004522.html
english.stackexchange.com/users/257/JoFrhwld
It follows the form
I <verb
> <rest of predicate>, and so can you!
For example, in I use computers, and so can you!
the "...
so can you" means "you can use computers, too."
The part where it becomes confusing, and funny, is that the verb is not an action verb, but "am."
So "...
so can you" means "You can be America too" in this case.
english.stackexchange.com/users/166/eds
It's a satirical joke.
The title is deliberately confusing, that's the whole point.
english.stackexchange.com/users/300/RegDwigнt
I always took "I Am America" to be hubris inflated for comic effect, and
the "(And So Can You!)
" part to be a backhanded slash at Americans who can't even speak their own language good.
english.stackexchange.com/users/161/Goodbye Stack Exchange
It's a joke on mistakes made with the English language by foreign countries.
If you look at the book there are many more jokes about the book being printed in some Asian country and it seems to make fun of engrish type mistakes.
english.stackexchange.com/users/687/jjclarkson
As a non-native speaker, I found Stephen Colbert’s book title I Am America (And So Can You!) a little hard to dissect. Why so can you? Why isn’t it So Are You ? What’s the full phrase that And So Can You implies?
Please explain "I Am America (And So Can You!)"
english.stackexchange.com
<grammar><phrases><book-title>
english.stackexchange.com/questions/1864
english.stackexchange.com/users/165/grokus
The title "I Am America (And So Can You!)" appears to be a play on titles from self-help programmes and functions as a satirical joke. The title is deliberately confusing and is a reference to mistakes made with the English language by foreign countries. It's a joke based on the language used in self help program titles.
The title "I Am America (And So Can You!)" appears to be a play on titles from self-help programmes and functions as a satirical joke. The title is deliberately confusing and is a reference to mistakes made with the English language by foreign countries. The title is deliberately confusing, that's the whole point. It's a satirical joke. It's a play on titles from self help programs which utilize ellipsis.
The title is deliberately confusing. It's a joke on mistakes made with the English language by foreign countries.   The title is deliberately confusing as a joke about the use of English in foreign countries.
It's a joke based on the language of self help program titles. IT's a satirical joke with a title that is deliberately confusing. It's a joke based on mistakes made with the English language by foreign countries. 
It's a play on titles from self help programs which utilize ellipsis. It's a satirical joke. The title is deliberately confusing, that's the whole point.
The title is deliberately confusing as a joke about the use of English in foreign countries.