We are planning our first cross country trip in a 32 foot travel trailer

we have 2 weeks to get from WNY to San Francisco Airport

Itinerary:

Buf to Iowa : Corn Palace

Badlands

Mt Rushmore

Crazy Horse

Grand Teton (?)

Lake Tahoe (?)

Yosemite

San Francisco

The reason why Grand Teton and Tahoe are in ? is because those dates will be around the 4th of July and will be crowded.

Our daughter is leaving from SFO and we will continue on from there

Any suggestions / insight would be helpful

The only reservation we have is in Petaluma (KOA) the night before and after the SFO airport departure. We did join KOA and Good Sam ...

Thank you so much!

What is your tow vehicle? The Corn Palace that I know about is in Mitchell South Dakota which is within a few hours of the Badlands.
Buffalo to South Bend IN is a good day drive. Get through Chicago and into Wisconsin on the second day.
Leaving Rapid City plan to spend a night near Cody WY. Between Rapid City and Cody you may want to visit Devil's Tower if the weather is good.
Do your have experience driving through big cities like Chicago with a 32 foot trailer?
If you really want to visit Iowa, it might make more sense to drive through it on the return trip.
Good luck on finding a camping spot anywhere in Yosemite in July.

When you're at Grand Teton, you are so close to Yellowstone, why not a few days there?

Sounds reasonable. As the previous poster suggested, Yellowstone should be on the list as well since it is only 1 hour away from Grand Teton and will be a memorable place. Yosemite is pretty but you will probably miss the iconic waterfall by the time you get there.