score:9
I wouldn't chance it.
You can look up expected CBP wait times to see how long the immigration process might take. Around 8pm, it's not uncommon for it to be on the order of 15-30 minutes, but some days it seems to be stretching to 30-60 minutes. If you have checked bags, you may have to wait longer to claim them. You must collect your checked bags, take them through customs, and then hand them back to an airline agent.
On top of that, you'll have to get to terminal 1 (all international arrivals come into terminal 5) and go through security. Terminal 5 is a bit of a distance away, and making matters worse, the train connection between terminals is closed for maintenance everyday except for Saturdays and Sundays, so you'd have to go outside and get a bus if you're doing this on a weekday. And then you need to get to your gate before boarding closes.
If you're coming from one of the US Preclearance airports, you'll go through US immigration before you board your first flight, which would provide you with much more time in Chicago.
It's not completely impossible if everything is on time and the lines are short, but I wouldn't book this. The biggest reason is that you're connecting to an infrequent international flight. If you miss it, you're probably waiting until the next night to get on a new flight. And any kind of brief delay at any number of places could be enough to miss it: a few minutes extra for your flight to arrive, at immigration, baggage claim, customs, the shuttle bus, or security.
Upvote:2
As a US citizen I would be very reluctant to book such a ticket. I have had such a booking through a California airport (Los Angeles IIRC) that a travel agent made and I yelled about when I saw it--and got it changed.
We cleared both immigration and customs reasonably quickly. While in theory we could have made the flight it would not have actually been possible because we would have missed the baggage check time by 5 minutes.
You also don't say where you are coming from but from your description I'm guessing Europe. Very long flights like that are always a bit variable on time because of variations in the jet stream. (Going between the US and China I see variations of an hour in the actual time in the air.) This is completely unpredictable, you get a strong jet stream that day and you no longer have an hour and a half to make your connection.