NEW YORK (AP) — A new, troublesome topic hovered over the St. Patrick's Day parade in New York this year: Britain's failed Brexit deal with the European Union that could squeeze Ireland's economy.

But nothing could put a damper on the largest American celebration of Irish heritage on Saturday, with tens of thousands of marchers following a painted green line up Fifth Avenue for the six-hour procession.

Kevin Coughlan, a 27-year-old spectator wearing pants with four-leaf clovers, captured both the New York celebration and the political near-catastrophe overseas, where he still has plenty of fam...