I don't think it would have changed the eventual outcome, but you are right about the FG call just killing any momemtum for the Steelers at that point. The Pats are a much more balanced team than the Steelers, and should handle the Eagles with no problem, IMO.
Despite everything, the Steelers were in the position to eke out a W like they did against the Jets. Cowher's crappy coaching made that impossible.