I am planning a trip to the USA.How long will I need in these national parks/sites to see everything??

I will be there from end Feb – end May.
I am planning on visiting:
Monument Valley, Arizona,
Grand Canyon, Arizona,
Death Valley, California,
Yosemite Park, California,
Yellowstone Park, Wyoming,
Rocky Mountains, Colorado,
Mount Rushmore, S.Dakota,
How long will I need in each one to get a good feel of it? And are they all worth seeing??
(Im not planning on hardcore hiking/climbing, just nice scenic walks/tours)
I would really appreciate some help, Thank you!!!

You could spend your entire life in Yellowstone and only see 50% of the park.

That said… if you really want to see anything:
1 day for Monument Valley
1 week for the Grand Canyon and Death Valley
1 week for Yosemite
2 weeks for Yellowstone (just going here alone would be worth your entire trip… by far the best of them all)
1/2 week for Rocky Mountain Ntl Park
1 day for Mount Rushmore (you could skip this one and not really have missed anything in my opinion)

Ones that are really good that you missed:
Glacier National Park – Sweet.. about 3 days would be good
Arches National Park and Canyonlands (about 3 days here too – not too far drive time from Monument Valley)
Great Sand Dunes national monument (not too far from Rocky Mountain Ntl Park 1 day)
Zion national park… there is a reason it got that name (1 – 2 days).
Grand Teton National Park (just outside yellowstone – 1-2 days)

Drive time between all of the parks will be significant… but well worth it.