Expert Flying is showing another AA flight LAX-LAS (AA2785) leaving at 19:45 with room in all classes.

That being said, this schedule change may allow you to also change you flight leaving (I assume is) LHR. Since this schedule change seems to be bellow MCT (last I checked it was 90 minutes for I-D connection), this usually opens the door to a lot more possibilities. Example: BA275 LHR to LAS direct departing 17:15 arriving LAS 19:55 with lots of room. Or connecting through other cities than LAX.

Remember also that you need to pick up and drop off checked luggage when connecting in the US from an International arrival.