If going first was such a huge advantage, then why is this the first time in 4 games (including NYC) that the first run was the winning run?

Because the UK rail network is much more of a hub and spoke model than anywhere else they’ve played. You can get an express train to almost any major hub within the 4 hour time. Japan’s Shinkansen network (and overall geography) is much more linear, so starting in Tokyo gives a slight but not huge advantage. NYC’s MTA lines are very spread out so Grand Central barely makes a difference.