I've had the U.S. version of haggis. I had always assumed that it had been cooked in a sheep stomach -- it certainly looked like one.
For the record, it was surprisingly mild and inoffensive. Don't think I'd want it every day, but a slice of it as an appetizer accompanied by a wee dram (or two), it wasn't bad. A slight liverish taste (since I'm OK with liver, no problem for me). But then, mine wasn't authentic.
I'll be going to Edinburgh this summer, so I may try the real thing.
Every year when the British Open is televised, we are reminded that the Scots say “If there’s nae wind, there’s nae golf.” Perhaps we should add “If there’s nae lungs, there’s nae haggis.”