I don't think very many other nations were sold on the idea. The information gathered didn't support the hypothesis. All that happened was that it expanded the national debt and ballooned budget deficits.
The idea was that if one cut taxes that deeply, then that would spur the economy's growth to such an extent that the tax revenues generated by the growth would offset those lost by the tax cuts. That didn't pan out. The economy didn't grow. It shrank instead.
Here is a snippet:
But as early as August 1981, Stockman (Reagan's budget director) began having gnawing doubts about his budget. Computer simulations failed to project the tremendous growth he had predicted, and later he would admit to cooking the numbers (!) before selling the budget to Congress. That December, the Atlantic Monthly published an article in which Stockman made several damaging and embarrassing confessions about the entire supply-side philosophy. He admitted that the 1981 tax cut "was always a Trojan horse to bring down the top (tax) rate" for the wealthy. Cutting taxes for the rich had long ago been coined "trickle down economics" - and it was an unpopular concept with the middle class. "It's kind of hard to sell 'trickle down,'" Stockman told the interviewer. "So the supply-side formula was the only way to get a tax policy that was really 'trickle down.' Supply-side is 'trickle-down' theory."7
The Rosy Scenario failed to materialize. The economy did not grow out of its deficits. In 1986, Washington and the rest of the nation would again be surprised when Stockman confessed all in a book entitled The Triumph of Politics: Why the Reagan Revolution Failed.
The rise of supply-side economics.