How do I get past this level in Call of Duty: Black Ops?

Okay guys and gals I'm on the WMD level in the game in single player, I have just destroyed the comms center and an RPG has just taken out a bridge. I jump across and start running, but then what? Half the time I fall off the cliff or the other half I die because I fail to stay with my team. What the hell? Any suggestions? What am I doing wrong? Please help.