Is it just that different to is British usage and different from is American?
Well – yes and no. I’ve gone through some quotation websites looking for 19th and early 20th century British examples and could find not one different to. They all used different from.
Here are two:
The Duke of Wellington in 1836: “It is very true that I have said that I considered Napoleon’s presence in the field equal to forty thousand men in the balance. This is a very loose way of talking; but the idea is a very different one from that of his presence at a battle being equal to a reinforcement of forty thousand men.”
Francis Thompson in 1908: “Know you what it is to be a child? It is to be something very different from the man of to-day.”
I did also find this, however, from the 1908 edition of Fowler’s The King’s English: “. . .different to is regarded by many newspaper editors and others in authority as a solecism, and is therefore better avoided by those to whom the approval of such authorities is important. It is undoubtedly gaining ground, and will probably displace different from in no long time; perhaps, however, the conservatism that still prefers from is not yet to be named pedantry."
Well, that certainly was prescient – if you concede that 100 years counts as “no long time.” (As they say: in England 100 miles is a long way and 100 years is a short time; in American 100 miles is a short way and 100 years is long time.)
Well, let’s do our best to keep The King’s English different from our own, at least in this regard – in honor of Mrs. Murphy.
P. S. Does anyone remember Richard Mitchell, the Underground Grammarian? Look him up.