Few impressions here as a Brit who woke up the NBC footage at the top of my youtube algo (thanks for the spoilers in the titles too), and watches events like Indycar that Leigh commentates on:
1. He's commentating on track races in exactly the same manner as the Indy 500. "2 LAPS TO GO" doesn't quite hit the same when its - still very fast - 1500 runners rather than a car going 220mph, often backed up with camera angles/sound that add to the action and his commentary
2. US broadcasters (that do prepare) seem to HAVE to add in their anecdotes, stories, interview notes etc into the race. Kara seems really bad about it. "X told me before today's race that they're here for the win"... great, you've added literally nothing, and what's actually happening? Same happens during marathon majors.
We're definitely getting more of 2 in the UK now but there doesn't seem to be many US commentators that can just say what's happening and not insert something random/useless into a limited timeframe to talk.