Quebec doesn’t have expertise with the type of tumor she had:

Harding-Jones lived with an extremely rare brain tumour called a colloid cyst, one that neurosurgeons in Quebec admittedly don’t have the expertise to operate on, patient files show.

… an ultra-specialized brain operation to remove the tumour that is only available in New York’s Weill Cornell Medicine Brain and Spine Centre.

Canada doesn’t have the population density of the US. If a condition is exceedingly rare, patients occasionally need to go to elsewhere to find specialists.

I suspect Americans in less populous states would be in the same boat.