I have been on many JY USA tours including NY twice, people wear casual clothes and go for layers as the weather can change, you might want to put in a few bits that are smarter. I take a large case, but I put in a soft hold-all as well which then can go in the overhead bin on the plane, as I do like to buy clothes for myself and grandchildren along the way..
Have a great trip any questions just ask! ...
Cindy