I also love this tree. It is quite a change from the "deadwood here, jin there, curve there" approach to junipers that has made coniferous bonsai so predictable and boring these days.
The form you've chosen for this tree isn't as "live oak" as you may think--at least in my opinion. It may be that it is a neglected form of natural juniper styling. The broad crowned juniper isn't all that rare. Alligator juniper, for instance, grows quite wide and spreads --as do other species of juniper in the SW U.S.
http://aggie-horticulture.tamu.edu/...iperusd3740.jpg
The prevalence of form, not "style" is what you're after--at least that's how I've begun to look at it. I've pondered the "American" style of bonsai for quite a while. In the end, I don't think there really can be any particular national style. Trees adapt forms to different environments, not nationalities. The forms they assume are very similar when compared comparable region to comparable region, for the most part.
Pick up a copy of Charles Ceronio's "Bonsai Styles of the World." The styles he claims as "South African savannah" look very familiar to me as East Texas silhouettes...