There is no reason that certain stretches of US roadways should have speed limits. We could be just like Germany. The Autobahn isn't continuously unlimited speed; only certain sections are. Some as short as 5 km.
Well, maybe. I spent 2+ years in Germany in the Army -- er, um, okay, that was half a century ago -- and did a fair amount of traveling as fast as a Ford Cortina (owned by one of my buddies) could go. Fast Forward about three decades, and my wife and I did an Edelweiss "Best of Europe" motorcycle tour, which included some stints (the first and last days) on unlimited-speed stretches of the autobahn.
Of course, things may have changed in the ensuing five and two decades, but based on those experiences, it was my impression that the typical German driver was more attuned to the rules of the road than the typical American driver. I don't know, better driver's ed? Stricter licensing requirements? Societal view of driving as a serious activity?
If you're in the left lane here in the States, and someone in front of you had a momentary lapse of concentration, and hadn't yet spotted you in his rear-view mirror, and you flicked your left turn signal (a European thing) or flicked your high beams ... (whew) ... do you think he would understand that, and promptly move over? I dunno, but I've been behind plenty of left-lane drivers here -- on, say, the NY Thruway, and speeds barely above the speed limit -- who are oblivious to repeated flashes. All of which makes me wonder whether the US is ready for such stretches.
Back to TX -- and I'm guessing that
will know about this -- my buddy and I were on our bikes (he had an RT, and I was on my Victory Cross Country), going from Buda to COTA. This was back in 2013, and we had ridden from Albany, NY, to see the inaugural MotoGP races there. Anyway, I think it was TX 45 we were using to commute, and I think the speed limit was 85. In any case, I do remember that traffic on that was almost non-existent, and that I got to see if Victory allowed the cruise to be set beyond 100 (it did) on that road. So, OTOH to what I wrote above, maybe there are certain stretches that would be okay.
Oh, one last thing. It's my understanding from reading some articles over the years that Germany invests a lot of time, money, materials, and energy into building really good road beds, the sub-surface and suchlike, for the autobahn. That might make a difference, too, in terms of whether a road is suitable for high-speed driving.