The EES will collect digital fingerprints, a facial scan, and passport data upon entry and will flag those who have not left within their permitted visa time allotment in the EU (which for most is 90 days). In other words, the days of entering on a valid visa, then overstaying that visa, are coming to an end.
The U.S. does not yet have this ability – and currently, most of those in the U.S. illegally, have arrived on a valid visa, then overstayed that visa. Oddly, the U.S. media thinks if you’ve done this, you should then be permitted to stay forever – which sounds a lot like an “open borders” idea.