It’s far more than 11 million, 30 million is probably a low conservative estimate.
My father and uncle crossed the Canadian Border illegally around 1950. Dad got a great job working for the DOD making missile triggers in the San Fransisco area. One day immigration officers came around and knocked on the door. My uncle escaped through the back door, jumped in the car they had crossed the border in and high tailed it back to Vancouver. After a long day at work my father came home only to be greeted by immigration. They put him in jail for a night. The next morning they gave him an offer he could not refuse. He volunteered to go back to Canada and get back into line. He finally entered the U.S. legally in 1956.
How did Immigration find them? They took down the license plate number when they entered the U.S.. When they did not return, they looked and found them.
Now the Feds can't do, as my Dad would say, “_u_k $hit”.