Really, its true - trade can make everyone better off. A mistake most people make is to look at a slice of time, or a slice of people and ignore the huge effects that trade creates over time.
Yes, the workers at the textile mill that just closed down face a burden, some for a short period, some for a long. But everyone else (including themselves) have access to cheaper clothing - this makes us better off.
It is very hard to image with any confidence the way things would have been - but would we really be better off without all of those goods that China sells us for cheap? People get really angry when prices rise, why do they also get angry when prices decline?
Change is hard, but it incrementally gets us to a better place.