In America, car dealerships typically sit on 5-20 acre lots, carry an inventory of tens, if not over a thousand cars, in some of the largest dealerships. In many suburban markets "car dealership" is synonymous with "new car superstore". The number of customers buying a custom order is very likely under 10%, maybe even under 5%. If you even suggest ordering a car the sales person will (in my experience) try to steer you towards something that's on the lot, as they can close the deal that day and you drive home in the car you bought.

We met a Belgian Mitsubishi dealer once, he showed us photos of his dealership, the building was about the size of a McDonalds with three bays for service and a modest office area and parking for about 15 cars. Most everything was custom order. This is, as I understand it, pretty common in Europe, and how cars were sold about 70 years ago in the US, but the "super store" model has been in place in America since at least the 1980s.