I think we as fans make a mistake when we assume players' loyalties to a team operate the same way as ours. We typically adopt a team as children and remain loyal to them for life. Players are much more transactional, because they know that today's rival may be tomorrow's employer.
Look at James Harrison. He's played most of his career for the Steelers, but has also been on the roster of their three biggest rivals (Ravens, Bengals and Pats). You think when he puts on a Pats uniform, he feels any residual tug for the Steelers?
Or think of it in terms of your own career. Do you feel any residual loyalty to your former employers? Maybe some you do, others you have a bias against, but I bet in most cases it's simply a place you used to work.
Also, when a former player becomes an announcer, their incentives change. I guarantee you Collinsworth -- and Romo, and every other announcer out there -- is far more interested in his bosses at NBC thinking that he called a good game (which he admittedly did not do on Sunday) then he is in who wins. Not only that, but if his boosterism got in the way of his calling a good game, he might find himself out of a job. He need only look at what happened to Phil Simms to know that he is replaceable at any minute.