Most people boil too much water. Get a kettle that can take a smaller amount of water and then boil what you need. If that’s not good enough, you can get a kettle that keeps water warm and then you don’t need so much energy to boil it (or figure out a routine or trick to turn the kettle on earlier, eg a teasmade). If you want to throw money at the problem USB-C is not the answer (how does that even make sense??) but you could (a) get a 240V socket (eg NEMA 6-15) in your US kitchen and rewire a 15A 240V European kettle to the appropriate plug. Or get an impulse labs induction hob set. Their whole selling point is using batteries to be able to put more power into boiling water than they can get from the wall.