By Chris Smith Philadelphia Union head coach Jim Curtin has made the bold claim that Major League Soccer could be a ‘top league’ in the world by 2026. MLS has undergone a period of rapid improvement over the last few years, with more and more young stars heading to the league from South America, while some of Europe’s biggest clubs have begun shopping for players Stateside. The likes of Atlanta United and Seattle Sounders attract huge crowds, while Charlotte FC broke the MLS single-game attendance record in their first-ever home match back in March. Soccer is expected to experience a boom in N…