Why are so many Canadian Muslims traveling to the USA to attend the Sufi Majid in Waterport NY?
Truth of the matter, is that sufi is a branch of Islam which preaches an almost Buddhist approach to Islam. Sufi masjids are not as readily available as Sunni & Shia masjids. That might be a reason why they would cross the border in order to attend the sermon and prayer.
As well there is a little matter called "Freedom of Movement" which allows someone to travel from one country to another in order to attand such events.