Philipp -
No, it would be far better to tour the West.
And at 41, it should be a piece of cake for you.
I was 49 in the link I sent you - 60 when I did my last cross-USA.
I think you will find that you do more distance per day in the West -
simply because distances are so great. Kinda like a Tibetan prayer wheel.
Once you get going on a remote road - you just keep going.
On the linked tour, I hiked across the Grand Canyon, hiked deep into a number of wildernesses.
So, I enjoy hiking as part of m extended bike tour, also. Plus, I dislike big cities when touring.
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I noticed that there is one non-stop flight from Frankfurt to Seattle. Dpt - 12:25. Arr - 14:25.
Only 2 hours! Except that you gain 9 hours. So It will feel like midnight when you arrive.
The key is to stay up as long as you can - maybe until dinnertime.
I think a tour from the Washington coast to Glacier National Park in Montana then down the Rockies -
would be very possible - esp. given all the time you have. Heading south with the autumn season.
And I think you will have no problem with climbing - if I can do it, you can.
Just take your time and eat a cookie for every mile you climb. (That's a lot of cookies.)
In Colorado I would stay as far west as possible - far from Denver metro.
The mountains near Denver are its back yard - very developed, very busy.
That includes the Breckinridge section of the TransAm.
Far better quality of riding further west.
Also, you don't want to go as far as Pueblo - then it's tough getting to Albuquerque.
Rather, stay in western Colorado then head east toward Taos - another amazing place.
You will have lots of ups and downs in northern New Mexico - plus much more traffic.
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Are you interested in Native American cultures?
I did my doctoral minor field in Native American history.
There are some excellent opportunities throughout the West to learn and see a wide variety of peoples.
On the far northwest tip of Washington is Neah Bay the homeland of the Makah people.
The Makah Museum is amazing - with a near-complete Ozette village from pre-1700s.
The village had been buried under a mudslide - then uncovered by a another slide.
http://makahmuseum.com/Just east of Glacier N.P. is the Museum of the Plains Indians on the Blackfeet Reservation.
It is a relatively small museum with few visitors, but the collection is superb.
Fine buffalo robes, headdresses, photos and interpretation.
https://www.doi.gov/iacb/museum-plains-indianThe Puebloan peoples of the Southwest are another totally different culture.
If you can go off road some, the Chacoan ruins are unbelievable - rivaling Machu Pichu.
(You could also do that with your cousin from Abq, via auto.)
Other options would be either Mesa Verde N.P. or the Azrec Ruins N.M
Juan
PS - If you are ONLY riding from Washington state to Albuquerque -
then you will have plenty of time to deviate from a direct route and to explore.
Take the empty roads where you can hear the river on your right.