Ireland has very low tax rates so a lot of companies like Apple, Google have their corporate offices there to take advantage of it. Government's 95% of revenue comes from corporate taxes. Trump has desired to lower corporate tax rates to match Ireland's to help companies relocate back to US and start manufacturing there.
China used to send goods to Vietnam and then send goods to US (exploiting Loophole). With US announcing big tariffs on Vietnam, country's growing GDP and future may face speed breakers or even full stop if companies decide to move merchandise production somewhere else.