The tradition of visiting seven churches on Holy Thursday during Holy Week is especially popular in Italy, Poland, Mexico and the Philippines. It was brought to the USA by immigrants from those and other predominantly Catholic lands. Here is an example: the Polish Christians of New York continuing with the tradition. Watch a video on the traditional ‘seven churches visitation’ on Holy Thursday in Buffalo’s Historic Polonia (New York)

So where does this tradition come from?
Source:Seven Churches Visitation -Wikipedia 
Our Sunday Visitor

The Seven Churches Visitation also known as Visita Iglesia is a pious Roman Catholic tradition observed by faithful Christians during Lent by attempting to visit 7 Christian sites or parishes. Customarily observed during Maundy Thursday, today it is commonly practiced during any day of the Holy Week.

Various associations have been made during Lent with regards to the significance of number seven. Altogether, they range from the following:
Seven scriptural events of Jesus Christ’s capture
Seven Last Words on Mount Calvary
Seven Wounds of Jesus Christ (Five wounds plus Scourging and Left Shoulder)
Seven first holy Christian sites in Israel
Seven Deacons of the Twelve Apostles
Seven ancient basilicas of Rome