Placing an object in the distance of a car dash-cam recording.

Yeah, I pretty much concur with Rick and would go even further: This is most definitely going to be 70 to 90 percent manual work. the vibrations alone are a problem for any kind of tracker, not to speak of the lack of detail in the forest and on the track that would make it hard to latch onto any "features" for a tracker.

Mylenium

If that is the only copy of the footage you have, you will have to pre-compose a copy of the footage and apply some serious color correction to bring out as much detail in the shot as you can, then try to run Camera Tracker on the pre-comp in the main comp. Even if you have the original footage and the quality is significantly better, you will probably still have to add some color correction and detail enhancement to get the Camera Tracker to work correctly.

If you can successfully get a camera track, you can add a 3D layer with the image of the flagpole. You could even add a waving flag. The shot will be difficult to work with as is, and you will need an expert understanding of Camera Tracking to be successful.

You may have to do the keyframing by hand. It will be tedious, but it can be done. Before we had the Track Camera option, I did several composites by hand. A 7-second shot could take a couple of days to get right if you set keyframes every few frames. 

Rotobrush is not going to work for the windshield wipers. That will have to be rotoscoped by hand. It is also going to take some time.