The circuit breaker that is commonly used in the United States is the type that adheres to the National Electrical Code (NEC) standards. The most prevalent circuit breakers in the U.S. are those that are UL (Underwriters Laboratories) listed, which ensures they meet safety and performance criteria. The most common types include the following:

1. Single-Pole Circuit Breakers: These are used to protect a single circuit and are typically found in residential settings. They are designed to interrupt the flow of electricity when the current exceeds a safe level.

2. Double-Pole Circuit Breakers: These are used to protect two circuits simultaneously, such as in a 240-volt circuit in a home. They are essential for safety as they prevent the risk of electrical shock by disconnecting both hot wires.

3. Ground Fault Circuit Interrupters (GFCIs): These are designed to protect against electrical shock by quickly shutting off power when a ground fault is detected. They are particularly important in areas where water is present, such as kitchens and bathrooms.

The preference for these types of circuit breakers in the U.S. is due to the stringent safety regulations and standards set forth by the NEC. According to the NEC, all new residential electrical installations must use circuit breakers that are listed and labeled by a recognized testing laboratory, such as UL. This ensures that the circuit breakers are reliable and safe for use.

Data from the National Fire Protection Association (NFPA) indicates that electrical failures are a leading cause of home fires. The use of circuit breakers can significantly reduce the risk of electrical fires by interrupting the flow of electricity when an overload or short circuit occurs. For instance, in 2019, electrical distribution and lighting accounted for 43% of home structure fires, and 11% of these fires were caused by electrical distribution equipment, such as circuit breakers.

In conclusion, the circuit breakers commonly used in the United States are those that meet NEC and UL standards, including single-pole, double-pole, and GFCI circuit breakers. These standards are in place to ensure safety and reduce the risk of electrical fires and accidents.