I agree that your itinerary is awfully rushed. You'll be spending more time traveling than sightseeing.

Personally, I'd recommend cutting Philadelphia. Cheesesteaks and an art museum are available anywhere. You're going to see several of the best museums in the country in NYC and DC. Cheesesteaks are available anywhere in the USA...and having had a cheesesteak at one of "the best" places in Philly, I can say that they're all pretty much the same.

Better to spend an extra day or half day in NYC so you have time to do the myriad of things you want to do here - or use that time to enjoy LA and SF more. I'd also recommend flying to LA from Arizona instead of taking a train. Amtrak is not known for timeliness.

Finally, no matter how fast a walker you are, you will struggle to do all the things on your list as-is.