kamu bisa berbicara 沒 seperti belum; dan 不 seperti tidak atau bukan. semoga kamu bisa mengerti maksud saya....

Well, it does make sense for what your teacher had told you that 没 is used for complete action. So in the sentence 我没有去過美國, it means you haven't been to the U.S. in the past. However, if you switch it into 我不去美国, it sounds like you won't go to the U.S. for some reason. For example, after a terrorist attack on somewhere of America, you can say: 我现在不想去美国,which means you don't want/plan to go to the U.S. recently. Hopes this helps. :)

他唱的好聽嗎?→不好聽 他唱的有好聽嗎?→沒有 不=沒 沒去印尼 不去印尼 不≠沒 不=no 沒=nothing、empty 總結，很複雜，"有時會交叉用"，只有多說多感受語感=_=

沒 = you don't have 不 = you don't want i don't wanna talk about it 我不想談這這件事 i'm not talking about it 我沒有再談這個

不 have the meaning of refusal 沒 have the meaning of nothing(not have