Crime rate
Crime rates are not the same everywhere and high rates of crime tend to be focused in certain areas only. Despite the reputation of America as the "firearms murder" nation of the world, most areas of the country rarely, if ever, face criminal activity of this type.
However, fear of crime has had a major impact on American society, and has been used to exacerbate interclass and sometimes interracial tensions. There are times when fear is justified, but it is frequently out of proportion to the risk of encountering criminal activity. Many Americans are fascinated by crime in their country and this is reflected in the media coverage. It has been suggested that the saturation coverage of crime in America reinforces Americans' anxiety about other people and increases their fear of loss of loved ones and property.
Illegal activities
It may be wise to check local legislation as it affects you when you first arrive in the States. Of course, most 'obvious crimes' are crimes in America too, however, some states may have laws that catch you by surprise (curbside recycling may be mandatory in some areas for example).
Controlled substances
Illegal drugs and controlled medicines are subject to various penalties for possession, use or illegal marketing and distribution (drug trafficking).
Legal ages (sex, marriage, alcohol, driving)
The legal age of consent for heterosexual sex in most of the USA is 16 years, but the age of consent for homosexual sexual relations is 18.
The legal age for consumption of alcohol in many states is 21 years. In other states it is 19 and in others yet 18 years. This is higher than in many other countries. One should be sure to check the legal age for the state you are in.
The legal age to drive in the USA is 16 years. However, there are certain types of exceptions where the age limit may even be as low as 14 years.
Emergency services and numbers
The phone number to call in an emergency (i.e. for police, ambulance, fire department assistance) is 911
In virtually all telephone books government agency phone numbers are listed as well as both the emergency and non-emergency numbers for the police and fire departments. You should usually call the non-emergency number, but if your life, or another's life is in danger, then you should dial 911 (this also applies when there is a crime in progress). You must provide the operator with your location and if you do not speak fluent English, you should learn some phrases for emergencies and know how to pronounce an address so help can get to you.