How to calculate the current of a MCU and CAN BUS circuit?
Power budget:


SN65HVD23 datasheet table 8.3 - maximum current value 48mA (times two)
STM32F205RGY datasheet table 12 - maximum total current 120mA. This value probably assumes that totally everything is running at the same time. Your real consumption will be lower than that.
LED - 20mA


Total 236mA. 300mA LDO should be fine.