NEW YORK — India’s new prime minister, once shunned by Washington, appeared before an enthusiastic crowd in a famed New York sports arena Sunday where he appealed for help from Indian-Americans to help develop his country’s economy, vowing that under his leadership, the South Asian nation wouldn’t look back.A day after addressing a hushed U.N. General Assembly, where headphone-wearing delegates rarely break into a smile, Narendra Modi received a tumultuous welcome from upward of 18,000 people. He struck a chord by announcing plans to simplify the immigration bureaucracy for Indians living abroad, and called on them to “join hands to serve our mother India.”A dazzling, Bollywood-style show with dancers warmed up the crowd before Modi appeared. About 30 U.S. lawmakers attended — ringing the stage as the Indian leader came into the auditorium under a spotlight like a boxing champion. The event had the feel of a political rally, and the audience periodically broke out into chants of “Modi! Modi!”Modi will meet Monday with President Barack Obama at the White House, a meeting that both sides hope can improve strained relations between the world’s two largest democracies.Being courted by Washington marks a major change since 2005, when the U.S. denied Modi a visa for his alleged complicity in sectarian violence in his home state of Gujarat.