It wasn’t “designed for US citizens”. It existed long before the USA ever came into being. It is ancient. It was simply adopted and utilized a lot in America. Since more people from the USA seem to use it than other countries, more US laws have been located to authenticate it, but it can be equally authenticated in any country. It is used throughout the world. Everywhere, the natural law exists, and has pre-dated statutory law. It is the right of all human beings everywhere to enter into private contracts with each other . . . as long as doing so doesn’t violate the rights of anyone else. This is surely verified by numerous Supreme Court cases in most countries.
Also, although natural law instruments are better than statutory ones, in general, a good trust writer can usually also arrange for statutory entities to be set up if you need them — whether they be corporations, foundations, IBCs, statutory trusts, or whatever, in any jurisdiction in the world. And he should also be able to help you structure asset protection layering between them, if you wish.