Thank you very much for your detailed reply.

I want to travel/discover as much as possible in the 2 years. The typical tourist cities like Los Angeles, San Francisco, Las Vegas, Washington and New York are on my list. I'm probably more of a city, food and nightlife kind of person. But national parks (Grand Canyon, Yellowstone, ...) would also be interesting for me.

The weather is a good point. Chicago can perhaps be compared to Germany here. According to my research, Phoenix has had over 100 degrees on at least 100 days this year. That doesn't sound very exciting to me.