Differences

I've made a few posts here recently which talk to how the USA and Britain are different. But that's a subject which could feed a blog for years and years with boring posts. Check out Anglophenia if you don't believe me. So this post serves as a large flushing of some of the post obvious differences:

Item	USA	Britain	Rest of the World
Electricity	110 volts	220 volts	Mostly 220 volts
Measurements	US imperial	Metric (and UK imperial)	Metric
Baking measurements	Cups	Metric (and UK imperial)	Metric
Speed limits	mph	mph	km/h
Drive on...	right	left	Mostly right
Date format	mm/dd/yyyy	dd/mm/yyyy	dd/mm/yyyy
Head of State	Elected president	Monarch (but de facto: Leader of largest party in parliament)	Mixed
Paper	Letter	ISO* A4	ISO A4

* ISO stands for International Standard Organization.

Tell me which ones I've missed!
Some of this information could be fodder for future posts. What is the history of the US's unique date format, for example?