Do all American newspapers have these? The Guardian, which I usually read when I can bear it, has never carried more than two daily comic strips, both of which are political (Doonesbury on American politics and If... on British). I think that such strips in British newspapers, at least broadsheets, tend to be exclusive to the paper, not sold to many papers by syndicates as in the US. (E.g. Alex is a famous and popular comic strip which appears exclusively in the Telegraph, and the unnamed cartoon by Giles was exclusive to the Express.) It seems to me that non-topical, widely distributed comic strips in newspapers are quite an American institution and one which isn't reflected so much in other countries. Which is why the points about the episodic nature of the medium strike me as rather odd. I don't see anything intrinsically episodic about comic strips compared to other media. In a way, it's odd to think of the ones listed in the poll as episodic, daily media at all - I know Garfield, Calvin and Hobbes, The Far Side, etc. solely from books.
Of course, a lot of literature is like that, not just comics. Many nineteenth-century novels that we think of as single works were originally serials in magazines or newspapers, such as most of Dickens' output and some of Hardy's and Conrad's. Today we read them as integral novels but they were not originally intended to be read that way (and in some cases, such as Conrad's Nostromo, not only don't seem to know where they're headed half the time but even have sections ghost-written when the author was unable to meet his deadlines). I'm sure the same is true of these comics - although originally written episodically for inclusion in newspapers, future generations certainly won't read them that way.