Americans are giving up their U.S. citizenships in droves, but that Uncle Sam might still be lurking. After nearly two decades, the U.S. Treasury finalized a rule last year saying that certain individuals who surrender their citizenship or green card and give gifts to an existing U.S. taxpayer will create a tax bill for the recipient. Amounts above the annual $19,000 gift exclusion will generally be taxed at the highest estate or gift tax rate, which is currently 40%. Credits from foreign taxes paid, such ...