First of all great forum and lovely to see all the people helping.
Me and my wife are planing a 3 month trip from east to west. We read lots of information including an old post here of a similar trip but it is from 2009 so I believe things has changed :) this is why I would love and advice on most of the things were,when,what not? So far we are thinking to rent a car somewhere in Chicago or Detroit basically were is cheaper to do so or take a train through nearby cities to New Jersey and rent a car there (but we will be with large language so probably not) we know we want to visit most of the iconic places in America. Definitely Chicago - Boston - New York - Miami - New Orleans - National parks and California. We were thinking spend 2 months traveling to California and then explore it.
So what would you suggest? Scenic routes, what not to miss, were not to go, when is best time to go as we are flexible but were thinking around April next year.