If you wanted to protect a chopper against a jet, you would have to make it more or less a flying fortress, which would probably cause the chopper to be very hard to control, etc.
Helicopters as we know them do, without major improvements on stabilization systems, not stand a chance against jets. They are too slow to evade, yet, they can seek cover.
For urban warfare with own troops on the battleground there will always be something like a chopper: Slow, agile in movement and decent arming.
Jet's however will remain for bombing, where it's the natural need to 'do the job' and evade, speed is the way to success.