Breaking the appendix does not void your warranty. The seller must prove your modifications broke the device.
https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty...
https://en.wikipedia.org/wiki/Magnuson%E2%80%93Moss_Warranty...
The damages required for such issues can be quite high, $50-75k for federal court filing, but existing precedent would allow you to go after distributors in a local court for a lower amount.
But anyway: If I travel outside the US and buy a harmful appliance in a local shop, a US court would probably not take the case. Am I right? What would the manufacturer have to do to get exposure to US law?