1. Assuming you have BNO, you can enter US. You will require a visa to visit US.
2. Yes, you can drive in US with international drivers license.
3. Driving from Vancouver to LA will take more than 22 hours (unless you don't plan to stop for rest at all). It is a very long drive and you will have to stop for gas at least once or twice (even if not for food or toilet breaks).
4. I don't recommend catching the bus. There are many many stops and will take you a lot longer than 1 day to get to LA. And the ride is not very comfortable.