can i use usb-a with iphone 14

The iPhone 14 still uses the same Lightning port as most other older iPhone models for charging. It shouldn't matter what the other end of the charging cable uses ... either USB-A or USB-C. Not sure where you heard these rumors from.

The limiting factor is what your car's USB port is.

The USB would be used to interface to some other device for some reason.

You have asked us to guess both.

If the reason happens to be to charge the iPhone, yes that would work.