The main difference between a Master in the UK and the US is the duration of the program. Most MA programs in the UK last for a year while the ones in the US tend to last for two years. You are right, majority of MA programs in the US tend to be terminal yet that is not absolutely true as most well-known programs in art history are MA programs at Columbia, Williams, NYU etc. The same can be applied for the Courtauld Institute of Art, UCL, King's College etc., in the UK. Another important difference is finance, as programs in the UK are not as expensive in comparison to the ones in the US. Additionally, I would suggest you to look into Christie's and Sotheby's MA programs if you are interested into working at the auction house as they tend to employ many of their graduates. The way of teaching is obviously different in both countries, but these would be the main elements candidates take into consideration when applying to MA programs in the UK and the US.