美国公民在中国签证过期需要回美国重新签证吗?我美国护照上的2年多次往返中国签证还有2周到期. 必须在

还有两周到期，赶紧联络公安局出入境管理处，申请续签，还来得及。 在到期前把续签申请递交上去，等待续签期间，签证过期也没事，很快下来就可以。

[1] You are talking about "entry certificate". It is valid for two(2) years. As long as your "leave (visa) to stay" in China has not expired, it does not matter if your "entry certificate".

[2] Once you return to the States, your expired "entry certificate" is no longer usable.You need to apply for another two-year "entry cerficate" from Chinese embassy in the States.
[3] But while in China, you can always apply a new two-year "entry certificate" from Chinese authorities (Immigration office/Home affairs). Good luck!