Why does my car no longer look the same after rear bumber being replaced?

Thanks..did some research and found that aftermarket parts were used would this cause the look or fit to change?

It's not very many vehicles out there that haven't been in some sort of fender bender, so if it aint too bad you may want to just ride it on. Now, you dont have to settle for aftermarket parts if you want to pursue it!

Found out there is a factory extended bumper for the 2011 chevy malibu with the 3.6L engine which i have in my car that also goes with a certain muffler type and a different dual exhaust checked my original sticker too has additional price for factory upgrades. Whwn they replaced my bumper they did not use parts for my engine type with factory modifications.