I believe Amtrak stopped publishing on-time performance stats back in the late 2010s, but you can read about the causes here:
https://www.amtrak.com/on-time-performance
Aside from the Northeast Corridor, the Philadelphia to Harrisburg line, 98 miles of the Michigan line and maybe one or two other sections, Amtrak runs on lines owned by others, mostly freight railroads.
Depending on the service, I might be concerned about 30 min. If you get to Chicago in the morning/earlier after noon it's a nice place to explore. I have taken the train from the east cost to Seattle three times. All three times I had about a tour hour layover. Took the time to enjoy the city, although my bike was checked so I didn't have that to deal with. Maybe you can check it for a few hours at Union Station?