A tax haven is defined as anyplace thar has lower taxes than where you live. Sweden is a tax haven to Norwegians.
Yeah but unless you violate the US tax laws putting your money in the Caymens simply means that you get the pleasure of paying taxes both under Caymen Island laws and US law. It’s only if you cheat on your taxes that your taxes are lower. Some people put their money in the Caymens and then neglect to list the earnings on their US return. It’s easier to get away with that if it’s overseas because the feds can’t easily monitor compliance. But it’s still illegal. I assume that Romney doesn’t do that and assuming he doesn’t I don’t think the Caymens should be an issue.