I learned about this favorite devotion of Pope Francis from Kathy Schiffer.
He composed this prayer while Archbishop of Buenos Aires:
Holy Mary, full of God’s presence during the days of your life,
you accepted with full humility the Father’s will,
and the Devil was never capable to tie you around with his confusion
Once with your son you interceded for our difficulties,
and, full of kindness and patience you gave us example of how to untie the knots of our life.
And by remaining forever Our Mother,
you put in order, and make more clear the ties that link us to the Lord.
Holy Mother, Mother of God, and our Mother,
to you, who untie with motherly heart the knots of our life, we pray to you to receive in your hands (the name of person),
and to free him/her of the knots and confusion with which our enemy attacks.
Through your grace, your intercession, and your example,
deliver us from all evil, Our Lady, and untie the knots that prevent us from being united with God,
so that we, free from sin and error, may find Him in all things, may have our hearts placed in Him, and may serve Him always in our brothers and sisters. Amen.
She is particularly called upon when marriages are in trouble, all knotted-up. It would be a good devotion to spread in the USA right now. According to this resource, we have good reason to turn to Mary in this time of national marital crisis:
Over a period of 28 days, Wolfgang visited Father Rem four times and received advice from the holy priest, who was honored for his wisdom, piety and extraordinary intelligence. ...During their meetings, Wolfgang and Father Rem would pray together and venerate the Virgin Mary. On the day of their last visit together, September 28th, 1615, Father Rem had been praying in the chapel of the monastery before an image of the Virgin Mary ... When the two men met, Wolfgang gave his wedding ribbon to Father Rem. (In the marriage ceremony of that time and place, the maid of honor joined together the arms of the bride and groom with a ribbon in order to represent their invisible union for the rest of their lives.) In a solemn ritual act, Father Rem took Wolfgang’s wedding ribbon and lifted it up, while at the same time untying the knots of the ribbon one by one. As Father Rem smoothed out the ribbon, it became intensely white. Because of this happening, Wolfgang and Sophie were able to avoid a divorce and continue their marriage.