The correct answer is South Carolina.
South Carolina threatened to secede (aka leave) the Union after the Tariffs of 1828 and 1832 because these hurt the trade relationship between South Carolina and European countries like Great Britain. A tariff is a tax on an imported good. This increases the price of foreign goods. When a tariff is put on foreign goods, usually other countries are less likely to trade with different US states.
This is why South Carolina threatened to leave, as these tariffs hurt their trade relations with other countries.