ieExplains: What is the big deal about the Taoiseach's St Patrick’s Day visit to US?

The Shamrock Ceremony is usually held in the days around St Patrick’s Day. This year it will be on March 12.
After much worry that it might not happen for various reasons, US president Donald Trump yesterday officially invited Taoiseach Micheál Martin to the White House for St Patrick’s Day.
The long-held tradition of taoisigh meeting with US presidents has come under scrutiny given the Trump administration’s focus on trade deficits — with Ireland specifically named in the president’s crosshairs.