Because the Dorcas Twelve Trees case exposed a great deal of information about the Wizarding World, marriage between wizards and Muggles had been considered illegal ever since.
However, America was not the first country to propose such a bill. As early as 1733, Perseus Parkinson, the British Minister for Magic, had already put it forward. It failed to pass, and he was swiftly driven from office, replaced by Cedric's great-great-great-grandfather as the new Minister for Magic.
European migration to the Americas in the seventeenth century made the conflict between the magical and non-magical worlds less acute in Europe, but it intensified rapidly in the Americas. The Scourers in particular multiplied at the end of the seventeenth century. After the Salem witch trials, the Magical Congress of the United States of America was established. They began arresting and trying Scourers, executing those guilty of murder, human trafficking, and torture. In other words, the Magical Congress of the United States of America was not the sort of place that treated Azkaban as a last resort. Even so, some notorious Scourers escaped capture. They formed families with No-Majs and vanished into the crowd.
By 1733, they should still have been alive, but they were primarily active in the Americas. What exhausted European wizards was not the issue of intermarriage.
First, one had to understand Britain's civil service system. It underwent a major reform after the Crimean War. Before that, a British prime minister would take office with a group of officials. These were not merely Cabinet ministers, but also certain "administrative officials." After the reform, their duty was to carry out the policies of the government of the day without participating in party politics. Before the reform, their appointments were all the prime minister's responsibility. In other words, when the prime minister changed,