Hi Fishin'
It probably was a national change, and I know their parent company is international, the same one that owns Baskin Robbins Ice Cream, etc.
I didn't realize the shape of the box was related to Krispy Kreme, the colleague who responded when I mentioned the change said that Krispy Kreme's boxes are like that, thus she hinted the change was made to compete with them. Cocidentally, Krispy Kreme broke ground building their first Boston area store, and had a promotional/mobile store open for publicity, etc.
Dunkin' Donuts was originally founded here in Boston, actually Quincy and its US corporate headquarters were in Randolph, Mass. Although this could have all changed recenty with how fast the corporate world moves, etc.
Brand identity is important though so I'm surprised they did this. Consumers are usually attached and loyal to a brand's packaging, etc. and generally as a rule don't like 1. Sudden change 2. Change copying a competiter. That's about all I got out of my marketing class in grad school (it was an elective, I was a PR/Communications major). We did a case study on Broch and Brach Candies...