U.S. citizens and residents must pay tax on their worldwide income. There is a limited exclusion for earned income (up to $103,900 in 2018), but there is no exclusion for gain on the sale of property abroad.
Depreciation methods that allow faster write-offs than straight-line rates in the earlier periods of the useful life of an asset. For example, in the first few years of recovery, MACRS allows a 200% double declining balance write-off, twice the straight-line rate.