Can I split (1) 220 line with a 30 AMP breaker into (2) 110 15 AMP outlets using 14/2 wire?
There are a few different issues here:
220 vs. 110
Or more typically, 240 vs. 120, but it is really all the same, so don't worry about that.
220 can mean one of two somewhat different things:

hot/hot - i.e., only 220. If you have only 2 wires (plus ground) coming from the breaker to the destination, you can't get 110V from it, or at least not without additional hardware such as a transformer. However, you might be able to simply switch from a double-breaker (hot wire from each breaker) to using just one of the breakers and attaching the second wire to the neutral bar in the panel.

hot/hot/neutral - i.e., 110V &amp; 220V in the same cable. If you have 3 wires (plus ground), then you are actually pretty well set. Then it becomes just a question of breaker size.


Breaker Size
You can't just &quot;change&quot; a circuit from 30A to 15A by using a lower-capacity receptacle and wire. You have to actually change the breaker, in this case from a double 30A breaker to a double 15A breaker. Though I would recommend switching to a double 20A breaker and using 12 AWG wire to be able to handle multiple loads better at minimal extra cost, while still maintaining full compatibility with devices designed to plug into a 15A circuit.
If you actually have 3 wires (hot/hot/neutral) and can change the breaker then you can install an MWBC. This shares the neutral between the two hots. But that can get a bit confusing. A better solution is a subpanel.
If you connect a small subpanel (it can be designed to handle a lot more than 30A as the existing 30A breaker will protect the existing wire), then you can easily support 4 15A 110V circuits instead of 2. The power comes in at 30A x 220V and the breakers in the panel go on one 110V or the other 110V 1/2 of the incoming circuit. You can even have a mix - e.g., a 220V circuit and multiple 110V circuits - in the subpanel. Each of the 110V circuits can be 20A using 12 AWG wire or 15A using 14 AWG wire.