The contents of a trunk kit will vary wildly all depending on where in the world you are. Or even where in the U.S.A. you are. Having just completed a coast to coast tour by car last year, I saw terrain and population go from urban to desert and mod things in between. Driving from Maryland to Atlanta Georgia was pretty much suburban interstate with continuous towns and cities. Even Texas from the border with Louisiana to Dallas and south to Georgetown was town after town, very populated. A vehicle breakdown or traffic accident would be no biggie there. Southern California was one large metropolis, so little survival gear needed there. Execpt maybe sun block and a beach towel.
The only place that was really bleak enough to rate some survival gear in the truck was southern New Mexico. Driving from Carlsbad south to pick up the interstate in Texas, there was a two hour drive through some real-estate that looked like the moon. We spent a month on the road, driving around to visit family, and see some sights. Being retired, we took our time and just went sight seeing. Aside from crossing Montana or Wyoming in winter, or Death Valley in summer, travel on American roads in the 21st century is a bit anti climatic. I think there is a valid need for an on-board first aid kit, a change of clothing,which if you're on a trip you have anyways, and maybe some car related stuff like a jug of coolant, a roll of duct tape, and a few spare fuses. A very small tool kit is a maybe. Certainly a car charger for the cell phone. Modern cars are now so complex, if you have a break down, you're not going to be able to anything by the side of the road. This ain't your daddies 1962 Chevy.
There should be a minimum of stuff on your immediate person at all times, anyway. Unless you're flying someplace, a knife should always be in a pocket. Small flashlight, fire source, some duct tape wrapped around an old credit card in the wallet, P-38 in wallet, and a few other odds and ends around in different pockets.
But in the end, it all really depends on where you are. Living in Montana in the winter will need a whole different truck kit than living a suburban Richmond Virginia. Heck, traveling north to Boston Massachusetts will require that you remove any material that the nazi like police in New Jersey will bust you for given any reason to stop you at all. Going to New York city for a over night to take in show and a five star restaurant meal means travel by train from Washington D.C. to NYC, so no car required. But AMTRAK has it's own security, so you have to pack carefully.
There's no set in stone trunk kit components, it all depends.