这句话的that是引导同位语从句吗?

问题描述:

这句话的that是引导同位语从句吗?
When reformers in the northern states put pressure on Congress not to permit slavery in western territories ( that) later became states,some of the southern states wanted to secede,or withdraw,from the United States.
这里的that引导的 later became states是同位语从句吗?
还是引导定语从句呢?感觉应该是定语从句,that 在定语从句中作主语。

当在北部各州的改革者向国会施加压力,不允许在西部领土实行奴隶制,(即)后来的美国,一些南方各州想脱离,或从美国撤出.
不是同位语从句,是定语从句,that 指代的是 western terriories感谢回答!可是还有一点不明白,that在这里不是做定语从句中later became states的主语吗?正好是从句中主语的位置呀,如果是同位语从句的话,that应该只起连接作用,不能做句子成分的呀?那就是了,既然在同位语从句里面that不做句子成分 ,那这里就一定不会是同位语了