Question

I am so happy that you could come to America with us for tha

Answer 1

Me too用处更加广泛，前句可以是Be动词或其他动词，比如：

I have a brother. Me too!

I am hungry.Me too.

So am I只能用于前句话有Be动词的情况，比如：

I am sick. So am I.

He is clever. So am I.