The city of St Catharines, Ontario, is not named for the Great Martyr, but rather
The city is named after Catharine Hamilton, wife of Robert Hamilton, an influential merchant of Queenston and a landowner with mills on Twelve Mile Creek; the growing community, then known as The Twelve or Shipman's Corners, was renamed in her honour after her death in 1796. (source)
Whether or not she was a saint, I'll leave in God's hands.
However, at least two churches in the city are named for the Saint: St Katherine (Greek Orthodox) and the Cathedral of St Catherine of Alexandria (RC).
And yes, all the varieties in spelling creates a never-ending problem.