The main thought is: Wow!
When American's say things are bigger and better over there it isn't just hyperbole. There is little in England to compare with the sheer scale and violence of American geology and the scenery it throws up.
It turns out the Colorado Plateau - which covers much of Arizona and Utah - has an average elevation of 6000ft, so we shouldn't have been surprised to get a good 2ft of snow in our first stop on Rte 66 in Flagstaff (twice as high Ben Nevis).
Fortunately the roads were soon clear enough to get to Sedona (Good Morning America's 'most beautiful place in USA') - nice!
Then it was north to the Grand Canyon - which is, indeed, as Grand a place as you can imagine...no, grander. It's too big to talk about, too big to think about - a mile deep, all carved by that biddy bit of water you see in the picture.
Monument Valley - based in the massive Navaho Nation and home to 300,000 Native Americans... only ONE of whom I reversed the hire car into in a parking lot - will be familiar to you from dozens of movies - from the iconic images of classic John Ford westerns to the latest fantasy romp John Carter.
But we had the best view: from The View hotel, the only one there. And we did the 17 mile dirt road drive through it... but don't tell the hire car company, they're already pissed off about the parking lot.
Heading into Utah, we stayed near Lake Powell, created by the Glen Canyon Dam. Upstream of the Grand Canyon, it took 17 years to fill and provides power and water to five states.
Heading further into Utah, we visited two extraordinary national parks I'd never heard of until some friends went there last year. The first - Bryce Canyon - is one of the maddest places I've seen. It's a giant ampitheatre full of multi-coloured eroded pinnacles called 'hoodoos' - some 60ft high. This is probably where the word 'awesome' was invented.
And just when we thought we has seen enough gob-smacking rocks and crazy canyons, we popped into Zion Canyon for the afternoon. The road into it from Mount Carmel was like a journey on another planet, and the Canyon itself was stunning. It was the place I least wanted to leave, but we were due in Las Vegas... which is a whole other story.