At the end of the second round of the US Open, a cut is made to reduce the field for the final two rounds. The US Open cut rule is determined is a little bit different than the three other majors and from week-to-week on the PGA Tour.
The US Open cut line is that the top 60 players and ties make the cut. There is no 10-Shot Rule, which would also include any player within 10 shots of the lead.
The US Open cut rule is among the strictest in the majors. The PGA Championship cut rule is to the top 70 and ties, while the Masters cut rule is to the top 50 and ties, meaning more than half of most Masters fields makes the cut. The Open Championship cut rule is also to the top 70 and ties.
Week-to-week, the PGA Tour cut rule is to the top 65 players and ties after two rounds.
The US Open cut rule doesn't account for a difference between professionals and amateurs. They're treated the same by the US Golf Association.