Hello. It is usually safe to assume it is simply the GPU.
Furthermore, your power supply has only a single 12V rail. Your computer would not have booted at all, and everything else would have burned, including the motherboard, if the 12V had failed.
Power supplies of that quality have over-voltage protection and over-current protection. It will simply close down if your video card fails, before anything is damaged.If your PSU would have failed, the over/under-voltage protection would have prevented it from working.
If you have a spare PCIe card, you can always confirm if your PCIE port is damaged, but I seriously doubt it.