-Yes, it will be automatically invalid.
可是移民局怎么知道呢?
-When you leave US, you need to provide the I-94 and thus, USCIS will have the record of your leaving.
我需不需要通知移民局我不要h4的申请?
-You had better not withdraw the H4 application, otherwise you may be out of status for that period of time.