This is an long running post of days ago but it is the first for me. I did not read through 5 pages of comment so I apologize before hand if it duplicates someone else's comment.
If I understood the OP, correctly, why would you want to even do that? European power supply is 240V at 50Hz. No telling how the heating element perform and if it has any electronics in it, what will happen to them. I'm no engineer but I would think the heating element will run a little hotter that could degrade the heating element because it may be operation out if its design element.
Keep in mind, my comments are based on only the OP
Well 240 V (US live-to-live in a 120/240 V 3-wire setup) is slightly higher than 230 V so in theory a US supply running at the upper permissible voltage limit might exceed the kettle's rating of 230 V + 10%. That would indeed cause the element to run hotter and possibly fail prematurely. However, I have no idea how much of a detrimental effect this would have. Probably none - I haven't heard of any equipment failing when the nominal voltage was increased from 220 V +/- 10% to 230 +/-10 % back in the 80s and 90s in most European countries.
Kettles usually don't contain any electronics and are a purely resistive load, so they couldn't care less about frequency, you could probably feed them DC. All that's in there is a heating element and a switched thermal cutout that shuts the kettle off once the water boils.
Actually there's a fun video of two Brits connecting a kettle to medium voltage - it lasts fine up to 8 kV instead of 230 V and only explodes at 10 kV! Water boils in an instant at 8 kV! Maybe 240 V + 10% would make your element fail after 20 years instead of 25 but to be honest the switch is likely to fail long before that.
