There is much to see in the Northwest USA.
From Seattle, you can drive across Washington to Idaho and Montana. You can go north to Glacier National Park then south to Yellowstone National Park and Grand Teton National Park. Yellowstone is a wonderful place with many strange and interesting geological features like geysers, hot springs and mud volcanos. Grant Teton is a small but beautiful mountain range with a very nice ski resort and cowboy town at Jackson Hole, Wyoming. From there you can drive south to Salt Lake City and through the canyondlands of Utah to Monument Valley. This will be a lot of driving. It is nearly 2,000 miles or 3,300 km from Seattle to Monument Valley. There are many things to see in the area of Monument Valley. Arches National Park, Canyonland National Park, Escalante and Capital Reef are all nearby. Even The Grand Canyon, Zion and Bryce Canyon are not far. I don't think you will have time to see everything.
When you have seen Monument Valley, the drive back to Seattle will be another 1500 miles or 2500 km. I hope you like to drive, because you must go a long distance by car to visit all these areas.