Here's a link. The key figure is one Prince Madoc.
http://www.welshdragon.net/resources/myths/madoc_usa.shtml
"Is truth stranger than fiction? Of course it is; it always has been One subject that has been debated for the last four hundred years was whether or not a Khumric-Welsh Prince called Madoc discovered America. Queen Elizabeth I was persuaded by her advisors that this was so and the Khumric-Welsh discovery was put forward as somehow giving England a prior claim in the political wrangles over first rights in the New World of the Americas."