@Bryan46 to your specific question : (a) there is a US-China Tax treaty --you will find this at---> https://www.irs.gov/businesses/international-businesses/china-tax-treaty-documents
(b) article 6 and 12 deal with definition and the taxability of gain from sale of real property etc.
(c) Article 22 covers method of elimination/reduction of double taxation.
What all this means is 1. when you sell assets in China, as a citizen/resident of US , you taxed on the gain by China under its laws at the time. US then recognizes this as a credit ( foreign tax credit / deduction) against US liabilities. Note that all US is required to do is recognize the taxes paid to China, not exactly how -- US will use its normal foreign tax credit ( with limitation for the year ) / deduction rules.
Also at these levels , you would have to file both FBAR ( FinCen 114 and FATCA ( IRS 8938 ).
Given the amount of your gain, I would highly recommend services of a CPA/ Tax professional familiar with international taxation to allow you to recoup as much of the foreign tax credit as you can -- selling all together will attract IRS attention and definitely you may not be able to recoup all your foreign taxes paid -- please consider this.
Is there more I can do for you ?
pk
