Question

为什么'如果我是你'是If I were you呢?

Answer 1

如果我是你’是一种虚拟语气，因为压根我就不是你。对于现实的一种假设，这种语气be动词的使用就是要变成were的，动词就变成过去式（我说的是对现在）。
If + were/did ，主语 + would/might/should/could + do(表示对现在情况的假设)
If I were you, I would not be so proud.
如果我是你，我会很骄傲。
If I had a cellphone, it would be convenient for me to get in touch with others.
如果我有手机，联系别人就会很方便。
If I were in your position, I would think better of it.
如果我处于你的位置，我会往好的方面想。
If I were her, I would apologize first.
如果我是她，我会先道歉。

Answer 2

因为我不可能是你，所以这么说句子要用虚拟语气。
对现在情况的假设:表示现在实际上并不存在的情况。其形式如下：

If主语 were+（表语），主语 should/would/could +动词原形
或
If主语 实义动词过去式+...，主语 should/would/could +动词原形
或
If主语 should do...，主语 should/would/could +动词原形

例如：
The platform would collapse if all of you stood on it. 假如你们都站在上面，这个平台会塌下来的。
If Lu Xun were alive，how happy he would be to see the great achievements of New China! 如果鲁迅还活着，看到新中国的伟大成就他会多么高兴啊！

Answer 3

虚拟语态，对现实的假设，因为我永远不可能是你。

Answer 4

不是事实were
是事实was

Answer 5

虚拟语气的用法