If you are a US person for tax purposes (citizen, green card holder, or resident alien) then you file your tax return according to US laws no matter where the income was earned. In this case, you have a capital gains transaction and you will pay capital gains tax if you have a gain (selling price more than cost basis). This will be on schedule D and form 8949, and all versions of the turbotax program on Mac or PC, and the Premium version online, will automatically include the forms.
Your gain is the difference between your selling price and your adjusted cost basis. There are some adjustments to basis allowed, but your travel costs are rarely allowed as adjustments, especially if this was not income-producing property. Cost basis is discussed here.
https://www.irs.gov/pub/irs-pdf/p551.pdf
If you pay tax on the same income to a foreign government, you can claim a deduction or credit to offset the taxes on your US tax return. Assuming that both countries calculate capital gains in the same way, you will either pay 15% or 20% in the US. Your credit will never be more than your US tax would have been. For example, suppose the gain is $100,000, your foreign tax is $20,000 and your US tax is $15,000. Your maximum US credit will be $15,000.
Also beware, not all countries calculate taxable gain in the same way. For example, some countries allow a cost basis adjustment for inflation, the US does not. You calculate your foreign tax according to the laws of that country, and you calculate your US tax based on US tax law, even if the methods for calculating the gain, basis, and adjustments to basis are different.
