Ordinary sockets in a UK home supply ~240 volts at up to 13 amps = 3kW of power. In comparison a typical US outlet is ~120 volts (can be 110, can be 120, it varies) at up to 15 amps = 1.8kW.

In both countries a home will have some beefier power for special purposes. In the UK (unless it's a really big house) this would be different sockets rated for more current at 240 volts or just stuff wired permanently for the higher current. e.g. an electric oven might be 20A at 240V = 4.8kW.

In the US the weird way they get 110V means most homes (except maybe smaller dwellings in a multi-residence building) get 2x opposite 110V supplies so you can do 220V (which may be closer to 250V in some cases, again it varies) by wiring across the two sides to deliver power for an oven or central air conditioning system or other power hungry equipment. Again this is either wired in or uses less common sockets so that you don't plug the wrong stuff in.

I believe the US is fully standardized on 120V and 60Hz for quite some time.

> In the US the weird way they get 110V

As a US resident I'm genuinely curious - what do you find weird about how we do the conversion from three phase? Doesn't the UK use three phase for transmission as well? Or is it three pole single phase itself that you find weird?

> uses less common sockets

Three pole single phase outlets are fully standardized in the national codes the same as 15 and 20 amp outlets are (https://en.wikipedia.org/wiki/NEMA_connector). NEMA 5 and 14 (previously 10, deprecated for 15+ years depending on jurisdiction) are the only outlet types I've ever encountered in a home.

Although the nominal power is standardised, for a variety of reasons the actual voltage of your supply will vary within agreed ranges (and this is true elsewhere). Frequency shouldn't change because it's a problem for the power plants if they can't agree on frequency.

Having three phase transmission isn't weird, it's the three pole single phase. There's no reason to do that except it's too late to change it now.

The argued upside seems to be that it makes household electrical systems less dangerous (reduced voltage). But if you care about that you'd design the rest of the system to be less dangerous as they did across Europe. For example, obviously the last few millimetres of the live pins of a plug should be insulated, you don't need them to conduct power and a human might touch them, so insulate them.

The point wasn't that these higher power sockets aren't standard (the NEMA standard is rubbish but it's a standard) but that they are literally less common.