You would have spoken up if it was me.

这句话可以理解为：

如果换成是我的话，你早就会站出来说话了。

或者更自然：
要是这事发生在我身上，你肯定早就替我说话了。

重点 1：speak up ⭐⭐⭐⭐⭐

speak up 是非常常见的口语短语：

speak up = 站出来说话、表达意见、替某人说话

例如：

You need to speak up.
你得说出来。

Why didn't you speak up?
你为什么不站出来说话？

She finally spoke up.
她终于站出来说话了。

这里的 spoken up 是 speak up 的过去分词：

speak → spoke → spoken

重点 2：would have + 过去分词

would have spoken up

这是一个非常重要的虚拟语气结构：

would have done
= 本来会…… / 早就会……

这里实际上是在说一个没有发生的假设。

You would have spoken up...

= 你本来会站出来说话……

重点 3：if it was me

if it was me

= 如果是我 / 如果换成我的话

严格的正式语法有时会说：

If it were me

但在日常口语里：

If it was me

非常常见。

整句话的情绪

You would have spoken up if it was me.

真正的语气可能是带一点埋怨：

“要是换成我，你肯定早就替我说话了。”

也就是说，说话的人认为对方对别人比较宽容，但如果事情发生在自己身上，对方一定会站出来。

可以把它记成一个非常实用的句型：

You would've done X if it were/was me.

= 如果换成是我，你肯定会做 X。

例如：

You would've helped me if it was me.
如果是我，你肯定会帮我的。