UK and USA are two countries separated by a common language. British English has tried for the most part to keep the spelling of the words it has borrowed from other countries. American English however has tried to adapt the spelling of theses words to the way they are pronounced in English in an effort to make spelling easier.
1) -ae- vs -e-
Many words that come from Ancient Greek have an –ae– in British English but only –e– in US English. Most of these words are scientific, medical, or technical words.
2- Double consonants
Sometimes British spelling requires a double consonant, for example in the past participle of certain verbs, where American spelling omits it. In other places, it is US English that has the doubled consonant; in certain verbal infinitives, or to preserve the root word of certain adjectives.
3) -ence vs -ense
Many nouns that end in –ence in British English end in –ense in the US. UK English only uses –ense for the corresponding verb; for example, you can license someone to do something, after which they hold a licence to do it.
licence (noun) license
4) Final -e
On both sides of the Atlantic, English is famous for the “silent” –e at the end of many words. Where both American and British English have this, in words such as name, make, or have, it comes from an Old English inflection. But many final –e spellings come from French loanwords, where often the consonant before the final –e is doubled. American English tends to omit these in accordance with Noah Webster’s spelling reforms.
The words axe (UK) and ax (US) follow this pattern, though the word comes from Germanic (not French) roots. The word judgement (UK) and judgment (US) can also be taken as an example of this if we discard the suffix –ment.
5) -0e- vs -e-
Like –ae– above, British English preserves the –oe– digraph in words derived from the Classical languages, while US English has simplified it to –e-.
While there may be certain differences between British and American English, the key takeaway is that the two have more similarities.