Someone asked the question on a mailing list – why is kudzu in some places in the south, and not other places? I think it’s a combination of luck and location. It would be interesting to find the places where it was originally intentionally introduced, and map the spread from those places. That wouldn’t account for all of it, of course, but I suspect there would be a correlation to some degree. But it’s also a function of “it hasn’t gotten there yet”. I’ve seen one study that claims it is spreading at the rate of 150,000 acres a year. While it apparently spread by seed, that apparently isn’t the primary means of propagation/propulsion. A group at the USDA research center in Stoneville, MS was researching a fungus a couple of years ago that might help control the stuff. Haven’t heard anything lately.
BTW – it has a beautiful flower, it’s just difficult to see in all that green. I have a small pic of it here.