Canadian banks participated in the same activities, the difference was Canadian banks didn't underwrite vast quantities of junk residential mortgages and then trick the CMHC into insuring them.  American lenders used a mix of pressure and financial trickery to get independent bond rating agencies to stamp their mortgage backed securities as high quality.  For profit, privately held mortgage insurance companies but government backed ( if there were losses to cover) like Fannie Mae and Freddie Mac also played a significant role in making things worse.  Also companies like AIG added fuel to the dumpster fire by issuing credit default swaps to "insure" garbage mortgage backed securities like they were signing autographs for adoring fans.