For one thing, Americans can't spell properly, and are always dropping unappreciated letters, such as writing neighbor for neighbour, or re-ordering them, such as center for centre.
Canada, a bilingual society located both geographically and historically between Great Britain and the U. S., manages to blend the two, though American-created automatic spell checking drives us crazy because we have to manually re-educate the dictionaries!
For another example, Americans can't measure anything properly, sticking obdurately to a caveman-era system of idiosyncratic and illogical measuring units, originally inherited, ironically, from the British, while the rest of humanity, including the modern British, use the convenient, universally understood, and logically constructed metric system of units. Does anyone care or recall these days how many feet are in a rod, why there are 12 inches in a foot instead of, say, 16, or on whose royal foot that length was based?
And the last important difference is that British gentlemen usually providentially carry an umbrella when they are out during the day, while American gentlemen usually don't unless it's already rainong!
Finally, though the Americans don't like the subject raised, the British never had a period or area in the home country when or where every man carried a gun due to lack of trust in the community-organized system for maintaining law and order, together with the weird modern-day consequences that can flow from such a system