One of the most notable bits of the Glass-Steagall Act was the ban on deposit-taking commercial banks from owning or operating an investment banking/dealing business and vice versa. I really don't see how reinstating the act prior to the financial crisis would have prevented or mitigated it at all. Companies what were engaged solely investment banking/dealing showed themselves to be just as likely to collapse as universal banks (institutions engaged in both commercial and investment banking). Specifically, Bear Stearns, Lehman Brothers, and Merrill Lynch, which specialised in investment banking, were just as, if not more vulnerable than Citigroup, Bank of America and Wachovia.
At the same time, all Canadian banks were engaged in investment banking activities to some degree, yet none of them collapsed or needed to be bailed out. In Europe, almost all of the big banks are universals, yet a number of institutions proved to vulnerable, such as RBS, Fortis and Barlclays.
As I understand it, the major difference between Canadian banks and everyone else's banks was that Canadian banks were much better capitalised, and must less reliant upon wholesale funding in the interbank market. When investors were seriously worried about counterparty risk in the interbank market, they really exacerbated the credit crisis.