"Has anyone ever heard of this becoming an invasive in Kentucky?"

I hope your question is a genuine inquiry. Paulownia tomentosa is listed as a class 1 (most severe) invasive in KY.

Here is a link that might be useful: KY-EPPC

Good assumption :-)) As to invasiveness in Kentucky, see below.

Here is a link that might be useful: Paulownias in Kentucky

Yes, it is genuine - Some of the road cuts through the mountains are loaded with them. Southern KY is pretty, but it seems to be a magnet for invasive species - Especially kudzu. It is a bit disconcerting to see what used to be pretty forest growing up in paulownia, kudzu, and whatever else has escaped cultivation.

I saw the same thing going to Florida but it was in March. It must've been the same plants only further south and therefore earlier in the season. I thought they were Wisteria. I think Paulownia has darker purple flowers than those on 75.

Nope, I traveled on 75 on the way to Texas last week. They were those blinking paulownias all right. Can't tell people they are invasive. Too many people think they can get by with just one or two.....won't hurt a thing.

I've told this story several times- I had two ancient Paulownia tomentosas removed from the front yard of our new house in May of '07- before we even moved in.
I felt terrible that our new neighbor's first impressions of us were as tree killers, but it simply had to be done!
As much as I hate killing a tree, I am not a criminal.
The criminal is the IDIOT THAT PLANTED the damned things.

I had the roots ground out as deep as the largest grinder would go. The roots shoots that came up that year were horrendous- one every foot covering the entire yard. It was literally a daily chore to keep up with them- you'd cut them all then the next morning there would be another hundred of them 2 inches tall.

They came up again equally as bad in '08, all spring and summer.

In '09 they slowed down a bit on my property but began seeking new areas as I saw them in neighbor yards as well- not only on the adjoining properties but across the street.

Spring and summer of '10- three full years since I had the trees taken out- and I still got shoots.
THREE YEARS!
They slowed down considerably but I still had to cut down one or two every couple of days. They are impossible to pull.
They are one tenacious tree.

AND...
I cut more root shoots in the spring of '11!!!
Four. Full. Years. After the trees were removed.
This tree is the devil!!!

This is the very first year I have not seen one- five full years of diligently patrolling the yard with scissors to cut root shoots.
In a way you're gotta respect that degree of the will to live!

10-12 years ago, I noticed a lone - and very large - Paulownia tree growing in the woods at the north end of our farm. Had intended to go back with the chainsaw and girdle it and apply an appropriate herbicide. Never got around to it.
Was by there a week or so ago, hunting morels(didn't find any); the old tree had died and toppled over, a casualty, I'm presuming, of old age or the combined effects of the Easter freeze of 2007, the ice storm of 2009, and a 2010 tornado. There's now a veritable thicket of young Paulownias springing up under the current hole in the canopy - either root suckers or seedlings. I'm committed, this time, to nuking them out.
Haven't seen any Ailanthus on the place, but if I do, it also has an appointment with the chainsaw and some targeted Pathway herbicide stump treatment.

Can you believe that a few years ago, our most local arboretum had paulownia saplings in their plant sale?

It's possible that the seeds that produced the southern KY trees came from Paulownias planted for strip mine reclamation (for which Paulownias have long been touted). Apparently the same qualities which let them succeed as pioneer species in waste places allow them to grow on poor strip-mined land.

I wouldn't expect them to compete very well with species that dominate a mature forest.