I think Trump is using the idea of sending migrants to sanctuary cities mostly as a talking point, and it would be wrong to do it, not to mention impractical (hard-pressed and underfunded ICE is in no position to go out of its way to bus migrants to select cities in the midst of a real crisis at the border). That said, let’s not pretend that an influx of migrants isn’t a burden even to the most open, well-intentioned place, as Canada has learned.