Wow, nice find there! Highly recommended reading for anyone that doesn't know that much about the US Interstate system yet, American or not.
I remember when Montana had basically an unlimited day time speed limit "within reason" on the Interstate. We convoyed three cars across there including my 1977 Pontiac Trans Am and I'm not sure we ever went much slower than 80 mph, several stretches at 100 mph.
Anyway, back on tangent. You know, honestly, I think if I were in your shoes (viper), knowing what I know now, I think I would fly to Miami if that is where you need to land at, and then fly again to California (or maybe Seattle
Take the money and time you would have spent driving across the southern US and enjoy a more leisurely vacation on the west coast. You can still rent something and get plenty of driving in and plenty of sight seeing as well.
The point I'm trying to make is this is a VERY large country and you can see some of it fly by a window in two weeks or "stop and smell the flowers" once in awhile. You'll never see all of it or even all the "good" spots, not even if you had a month to drive around. Maybe it's time to think about narrowing down your agenda a bit.
Also, as RC45 said just the state of Texas alone is HUGE and will take you a long time to drive across. Also the terrain just doesn't change a whole lot for a couple thousand miles. Seen one big stretch of desert, you've seen them all, or at least it will likely seem that way at interstate speeds.
And I have only the smallest bias about the Pacific Northwest (I love it here!) I have nothing against any other state or region, I spent nearly 15 years driving the Interstates coast to coast, every winter was down on I-10, I've driven most of the 47,000+ km of Interstate and have crossed the borders of all the continental US at least once. There is something special to be found pretty much anywhere you go in this country, if you have the time to look.