Understand English:

1. Does not Apply

Subject to the provisions of Articles 15, 17, 18, 19 and 20, salaries, wages and other similar remuneration derived by a resident of a Contracting State in respect of an employment shall be taxable only in that Contracting State unless the employment is exercised in the other Contracting State. If the employment is so exercised, such remuneration as is derived therefrom may be taxed in that other Contracting State.

Above treaty clause means: 

Resident of China (resident of a Contracting State) making money in China, should not be taxed in US (the other Contracting State).
Resident of US (resident of a Contracting State) making money in US, should not be taxed in China (the other Contracting State).

for example, Chinese citizen with green card does not have to pay Chinese tax on their US incomes.

你的問題是：美國居民（resident of US）在中國獲得的收入，是否要在美國繳稅。 你的情況和你引用的條款不適用。

2.  Apply to you, you have to pay US tax, after certain treaty allowances.

3.  Is the same as 1, you lived in China more than 6 months, you claim yourself to be "Resident of China", therefore 1 applies.  Again, your question is about Resident of US, therefore 1/3 doesn't apply, but 2 applies.