US CUSTOMS coming back from the UK

Do you mean customs ( inspection of goods you are carrying) or immigration ( inspection of your passport)?

And where is the “ there” in your second question, about returning to Chicago? Are you flying from Scotland to Chicago direct, or through Heathrow?

On the same ticket or separate ones?

Do you mean immigration?

I am a frequent ORD traveler - terminal 5, all foreign arrivals. Just under 2 weeks ago, the lines for immigration looked as if 45 - 60 minutes waiting would be minimum. Previous trip, lines were not bad to my observation. I have Global Entry and won’t travel without it. With GE, I was off the plane (long walk to immigration from airline arrival gate) and outside waiting for a taxi home within 30 minutes of landing. Sometimes, I’m through faster.

If you connect to a domestic carrier, you must collect bags after immigration. Well marked as to what to do. Train connection to other terminals.

Any specific questions? Much depends on how many other planes arrive with yours and where the arrival gate is.

As has been mentioned, there are two parts to international arrivals......immigration and customs. (Americans for some reason combine it into one.)

Immigration--sometimes called Passport Control--is for people. Customs is for your stuff.

Just a quick correction to the post referencing Seattle. In Seattle, you pick up your luggage first, prior to passport control.
Four lines. Global Entry, Mobile Passport, US Passports, All other passports.

I’m a Chicagoan. Get mobile passport but expect it to be a mess when you get back and expect surly personalities at best from US Customs and Border Patrol.

You may wish to get an Uber rather than the Blue Line if you live in the city. I am not in the mood for CTA games after a long transatlantic flight and the fun of returning to the USA

Uber does not pick up at Terminal 5 as of 2023. You have to transfer to Terminal 2 - the only Uber pick-up point.

I have been quite pleasantly surprised on my multiple returns (at least one each quarter) from abroad during 2023 and 2024. There has been an increasing amount of order and signage as to dedicated GE and mobile passport access points vs standard immigration lines. In past years, I have literally had to shout "Global Entry" and cut in front of many confused folks to make my way through a sea of travelers milling about before even reaching the formed queues for immigration. Not recently, thanks be.