AA 1910 then UA 3376 at O'Hare
Cancún → Chicago → St Louis
Timetable, Chicago time
16:32AA 1910 from Cancún at the gate
11:00UA 3376 to St Louis leaves the gate
18 h 28 apart on the timetable, overnight
UA 3376 leaves 18 h 28 after AA 1910 arrives on the timetable: more than half a day, so not a connection we count.