USGA
The USGA is the American golf association that, together with the R&A, publishes the Rules of Golf worldwide.
The abbreviation stands for United States Golf Association. The association was founded in 1894 and is responsible for golf in the USA and Mexico. For you as a golfer in Germany the USGA is present mainly through two things: the Rules of Golf and the handicap system. Together with the Royal and Ancient in St. Andrews it maintains the official Rules of Golf, which apply worldwide, including on your home course. It also stages its own championships, among them the US Open.
Most of the USGA is hidden in your scorecard without you noticing. The system of Course Rating and Slope Rating with which the difficulty of a course is measured comes from the USGA model. The numbers on the card tell you how difficult the course plays for a scratch player and for a bogey player. Your course handicap for exactly this course is calculated from them. Example: a par-72 course with a rating of 71.2 and a slope of 128 plays harder than one with a rating of 69.8 and a slope of 112, even when the par is the same.
A widespread misconception: the USGA does not write separate rules for America. The Rules of Golf and the World Handicap System are uniform worldwide, and Germany is connected via the DGV (German Golf Association). Anyone who associates the USGA only with the US Open overlooks that its measuring and rules work directly affects every one of your rounds. You feel the practical effect in your handicap and in every handicap calculation.
FAQ
Do different golf rules apply in the USA than in Germany?
No, that is a widespread misconception. The USGA maintains the Rules of Golf together with the Royal and Ancient in St. Andrews, and these rules apply uniformly worldwide, including on your home course. So there is no American special rule you would first have to learn on a round in the USA.
What does the USGA have to do with your course handicap on the scorecard?
More than you think. The system of course rating and slope rating with which the difficulty of your course is measured comes from the USGA model. Those numbers on your scorecard determine how many handicap strokes you get on exactly this course. Germany is connected to this worldwide system via the DGV.
Is the USGA only the organiser of the US Open?
No, the championships are only the most visible part. The association was founded in 1894 and is responsible for golf in the USA and Mexico, similar to how the DGV is responsible for Germany. Its real everyday effect reaches you through the Rules of Golf and the handicap system, which directly affect every one of your rounds.