OK kids...let's be careful about the advice we give. First off, armydaughter, you posted a link to a document that is undated, and lists Cadet Command HQ as Fort Monroe, and lists ROTC regions at the end. This document is obviously many years old. Ag, Majors do matter. Offers are being made specifically for STEM majors, and if you receive one of these offers and subsequently change from a STEM to a non STEM you will lose a year of benefits. It's still not to the level of navy/AF, but "essentially null" is definitely not the situation.
So, to answer the question, Cadet Command is transitioning from using the old ADM list (the list in that old document armydaughter linked to) to a CIP list. I'm still trying to figure out the system, but what I do know is that I had to go to the school to find the CIP associated with the majors (Clarkson had the list and I found the person who maintained it), and I'm told Cadet Command knows what CIPs they consider STEM, but aren't releasing that information yet. You will need to work with your Battalion to make sure you don't decide to switch out of the major you were offered the scholarship for.
But, here's the bottom line. The PMS has some latitude to allow you to switch your major, so make sure you keep them fully informed. If you were coming to Clarkson it probably wouldn't be a problem switching, but things may be different where you are going.