It's of potential interest to us, actually. I don't know of any examples, nor do I know how you'd prove such a thing, but it opens the possibility that a comic was created outside the United States for sale at least partially inside.
Those worrying about trademarks might also find this of interest:
http://www.cartoonbrew.com/classic/who-owns-betty-boop.htmlThe decision could be overturned on an appeal, of course, but the upshot is that the Ninth District Court concluded that a trademark can't block the use of public domain art.