Yep. Something like 10 million visas a year for ‘visits’ to the US, with almost no follow up.
Visa overstays could be addressed with better computer systems.
There are probably many databases that would reveal them, if they were searched - credit cards, cell phones, etc., in addition to Government databases, like drivers licenses welfare or voter registration. I doubt that China has much of a problem with visa overstays.
Artificial intelligence applications could mine the data, and learn to track them down.
Also, penalties could be increased, and deportation policies could be streamlined.