British English typically does not put a period after an abbreviation. Dr, Mr, Mrs, Ms, and vs are all written without periods after them. American English puts periods after abbreviations. Dr., Mr., ...

The British cringed over new American accents, coinages and vulgarisms. Prophets of doom flourished; the English language in America was going to disappear.

British English uses organise, while American prefers to organize. Both are correct depending on the region, but using one consistently is important. The reason for this goes back to the 1800s.