Sentence Correction

The book was banned in the US, as were two subsequent books.
is it the same as:?
The book was banned in the US. So were two subsequent books.

my question is, these two sentence express the same meaning? The first book was banned, the subsequent books were banned as well.

The book was banned in the US, as were two subsequent books.
A> as were
B> so were

here, since the comma before the second sentence, we choose "as were" right?

I made up this sentence, not an og question.