How does 高出一大截 break apart in 交货时间延长好几倍，单价翻几番，残次品率高出一大截?
Base on the context, the sentence should be interpreted as

残次品率 = Defective rate

高出 = higher than

一大截 = by a great distance (by a great degree)


残次品率高出一大截 = The defective rate (in American made goods) (will be) higher than (the defective rate in China-made goods) by a great degree
截 refer to measurement of 'length' --&gt; 'distance' --&gt; 'degree'
The comparison between American made goods and China-made goods also apply to 交货时间延长好几倍，单价翻几番
(美国制造的商品与中国制造的商品相比:)交货时间延长好几倍，单价翻几番  = (American made goods compare to China-made goods:) The delivery time will be extended several times and the unit price will be doubled a few times