On (1), I mean that $16B worth of goods is 12% of US->China exports, whereas it is only 3% of China->US exports, meaning that if this continues to escalate in this manner it will disproportionately affect US->China exporters.

I will concede (2) was not well expressed. I just find it much much easier to imagine – due to differences in labor forces, natural resources, environmental regulations, etc. – a suddenly growing Chinese motorcycle industry than, say, a resurgent US steel industry.