Maybe because I know this as a place-name, St. Croix. It would certainly not be mispronounced where I live but I can certainly see it is difficult for visitors to pronounce it correctly if they don't know it.
Because I hear it all the time, it'd be another plate-name to me, grouped with
Austin,
Dallas,
Aspen,
Cheyenne, etc - all of which I loved at one point. So in short - I'm kind of liking this, for a boy without a doubt.