before 1927 it was not even possible
I'm not sure that's actually true.
a) Scarcity of car Radios. Almost all radios before 1930 used batteries, 2V, 4V or 6V Lead Acid for filaments. 60 x 2V small lead acid or 90 x Dry cells for HT! Cars rarely had a battery other than maybe a 1.5V ignition cell for spark while cranking, then the magneto powered ignition. The ignition was easily "suppressed" by suppressor spark plug caps etc. The radio was't powered of the car, being basically a repackaged home unit.
Interference has got VERY severe since 1990s:
PC SMPSUs that NEVER had filters or got them taken out later to save money after CE approval.
Powerline Ethernet. Illegal period if tested properly.
Electronic "Ballasts" replacing passive interference free chokes on Tube lamps and on CFLs (early CFLs used a choke in the special ceiling unit).
Phone chargers etc as per PC SMPSUs
LED lamp PSUs
Flashing christmas tree controllers (any type lamp)
LED lamps on Christmas trees even if not flashing.
Dishwashers, Dryers, Washing Machines changed from Mechanical sync motor programmers to CPU (issue partly PSU, but CPU leaking RF)
Shielding abandoned on PCs, Laptops, etc.
LCD and Plasma screen matrix drive (screen radiates unless transparent tin coated)
Screen back light PSUs
But the IoT uses up the WiFi channels faster as well as the PSUs and motors making interference, but most homes AM Radio is already usless and VHF-FM is increasingly getting home generated interference.
"Real" Car radios did exist from early 1930s, but still rare till 1950s. They used MECHANICAL switch mode PSUs at 40Hz to 120Hz (Vibrator packs) to get HT. Very well shieilded separate PSU boxes, often with speaker driver amp. From late 1950s they started adding a pair of Germanium transistors as a SMPSU, then as audio Out and running the rest of the valves off 12V. Then from about 1958 the first all transistor car radios appeared.