We got stuck heading into Brussels once and it was pretty tough - which applies to you, also - because you have so many cities on your proposed route. And cities in the U.S. are probably harder to cycle into than in Europe. The real issue with U.S. cities is often the miles of suburbs where the automobile reigns supreme. Quite often, the city itself has lovely bike routes through parks and along creeks.
Which cities on your route are definite and which ones just possibilities?
With five months you will have plenty of time to take longer, but better, routes.
I agree with the discussion about getting out of New York City - there is a ferry service to Highland, New Jersey where you can ride out to the Atlantic Ocean dunes. From the coast you can ride across Jersey to the Delaware River at Lambertville and then up the Delaware River thru NE Pennsylvania and the Finger Lakes Region.
Just want to make sure that your visa will allow you to leave the U.S. - into Canada - and re-enter in Michigan.
Detroit? Really? Getting across the Detroit River is tough - plus the city ain't no picnic. There are wonderful ferries across the St. Clair River to towns like Algonac. Similarly, Chicago is not easy to ride into from the SE, but has great bike routes from the north and then leaving to the west. You could take the ferry from Muskegon, Michigan to Milwaukee, Wisconsin and then ride south into Chicago.
It will be getting hot by the time you get into Iowa and Nebraska - and unless you have ridden in North Africa or Australia - you ain't seen hot until you bake in the Great Plains. That said - I've ridden across Nebraska many times - and your route looks like it's the Interstate/AutoRoute or the roads alongside of it. Would you like to see the Great Plains as they looked 200 years ago? Highway 92 from Arnold to Arthur is spectacular.
Here are cycling map websites for Iowa and Nebraska:
And an old photo from long ago in the Nebraska Sandhills.