Should I use American English to write to an American?

I tend to Americanise my U.K English when I write to people in the United States. For instance I write Faucet instead of Tap, Diaper instead of Nappy,Yard instead of Garden..(you get the picture..) What I would like to know is if it's really necessary for me to do this or do Americans like the way the English write? How often do communication problems arise between Americans and Brits?