Answer:
hi!
differences: britains drive on the right side, there is monarchy (queen Elizabeth etc.), the the coin is GBP, some words are different between American English and Britain English like queue/line autumn/fall, USA citizens are more Patriots then British ones.
similarities: they fought together as allies in WW2, Both countries have a great tradition of literature and theatre, with film and music becoming the most popular entertainment of the last 100 years or so. (you can add the colors of the flag if you want to change something too)