You always have to report and pay taxes globally as a US Citizen or Green Card Holder even if the amount is less than $100,000.00. If the amount is more, then you have an added form to file, Form 3520.
You calculate tax on the full gain on sale, even though taxes were taken out at time of sale.
So for example, Appraised value at time of sale is say $100,000.00. Sold for $150,000.00. Tax taken out is $10,000.00. In the US return, you would owe taxes on the gain ($150,000 minus $100,000 = $50,000). The tax paid in the birth country is taken as Foreign Tax credit.
Now you may have cost associated with selling the property, such as realtor/broker commission paid. This would reduce the gain on sale of property. So in the above example, it would reduce the gain from $50,000 by the amount of expense.
