You'd be surprised.
So far, the only real tests that have been done on this are now about a decade old, and to be honest, the majority of vehicles weren't severely affected. Then again, the testing levels, etc., were not ideal, nor were the numbers of vehicles tested very large. So basically, the idea cars won't work is really not based on much evidence. If you're curious, can read the report here if you like.
http://www.empcommission.org/docs/empc_exec_rpt.pdf
That said, the more modern cars depend on very delicate electronics, that are likely more susceptible to it, but again, no real hard data saying this for certain.