How many gallons of crude oil does a US oil well pump in one day?

Depends...

First all oil wells are rated in barrels (42 gal).

Some wells can produce hundreds of barrels of fluid per day. Some wells produce only one or less than 1 barrel of fluid per day.

The fluid they produce can also vary in the amount of oil they produce, some wells might produce a lot of fluid but its only 5% oil where the rest is salt water. While other wells produce pure oil and all in between. Some wells even actually inject fluids back down into the geological formation. Not every well you see is a producer.

You might have two wells 50' apart and they produce completely different amounts of oil. It all depends on the geology down where they drilled and luck since you really never know what is down there until you drill the hole.