You can in fact purchase right this very moment bimetallic temperature switches for nearly arbitrary voltage / current combinations.
Right.
Mouser (a general electric/electronic component distributor in the USA) has 'em on the shelf rated for 600 V, 50 A.
I'm sure that specialty distributors offer a much wider range.
I've opened up my water kettle before and it uses a little bimetalic strip to shut itself off once the water is boiling. According to the label it sucks 1500 watts and it's just shoving mains voltage through the heating coil.