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Right: In the USA, there has been a serious campaign to ban alcohol advertising from New York subway trains.

Background information

(The information relating to alcohol-related problems in Australia is largely taken from 'Preventing Alcohol-related harm in Australia: a window of opportunity', prepared for the Preventative Health Task force by the Alcohol Working Group including addendum for October 2008 to June 2009.  The index to the full text of this document can be found at http://www.health.gov.au/internet/preventativehealth/publishing.nsf/Content/tech-alcohol
The information relating to the United States was taken from 'Alcohol - Problems and Solutions.  The full text of this document can be read at http://www2.potsdam.edu/hansondj/LegalDrinkingAge.html)

The legal drinking age refers to the earliest age at which a person is legally allowed to buy alcoholic beverages.  This may be different from the age at which they are permitted to drink alcohol, especially in the privacy of their home. The legal drinking age varies around the world -  from countries in Europe where people may consume alcoholic beverages at a young age (generally 16 or 17) to states in India where the drinking age is as high as 25. Some Islamic nations prohibit alcohol consumption by Muslims, and others prohibit it by anyone.

Drinking behaviour in Australia
Almost three-quarters (72.6%) of Australians drink below levels that would incur long-term risk of harm. However, among young adults (aged 20-29 years), the prevalence of drinking at levels posing long-term risk of harm is significantly higher (16%) than among other age groups (see Fig. 3). This pattern of drinking is the equivalent of consuming 29 or more standard drinks per week for males and 15 or more standard drinks per week for females. Among Australian teenagers in 2007, this drinking pattern was considerably higher among females (10.6%) than among males (7%).
For persons aged 10-19 years receiving treatment for alcohol problems, the proportion treated has increased from 15%  to 23% between 2001-2002 and 2005-2006.
Rates of risky drinking in Australia peak amongst young people, and alcohol-related harm is substantial for both adolescents and young adults.  Drinking contributes to the three leading causes of death among adolescents - unintentional injuries, homicide and suicide - along with risk-taking behaviour, unsafe sex choices, sexual coercion and alcohol overdose. A recent study of self-reported harm found that drinkers under the age of 15 years are much more likely than older drinkers to experience risky or antisocial behaviour connected with their drinking, and the rates are also somewhat elevated among drinkers aged 15-17 years. Furthermore, initiation of alcohol use at a young age may increase the likelihood of negative physical and mental health conditions, social problems and alcohol dependence.

The situation in the United States
Though it is commonly believed that the minimum drinking age in the United States is 21, there are a variety of exemptions that make it possible to do so earlier.
The National Minimum Drinking Age Act of 1984 required all states to raise their minimum purchase and public possession of alcohol age to 21. States that did not comply faced a reduction in highway funds under the Federal Highway Aid Act.  However, it does not prohibit persons under 21 (also called youth or minors) from drinking. By 1987 all states had complied with the 21 minimum age law.
The term 'public possession' is strictly defined and does not apply to possession for the following:
An established religious purpose, when accompanied by a parent, spouse or legal guardian age 21 or older
Medical purposes when prescribed or administered by a licensed physician, pharmacist, dentist, nurse, hospital or medical institution
In private clubs or establishments
In the course of lawful employment by a duly licensed manufacturer, wholesaler or retailer. 1
Many of the states that have chosen to specifically prohibit alcohol consumption by those under age 21 have a variety of exceptions. For example,
Some States allow an exception for consumption when a family member consents and/or is present. States vary widely in terms of which relatives may consent or must be present for this exception to apply and in what circumstances the exception applies. Sometimes a reference is made simply to "family" or "family member" without further elaboration.
Some States allow an exception for consumption on private property. States vary in the extent of the private property exception which may extend to all private locations, private residences only, or in the home of a parent or guardian only. In some jurisdictions, the location exception is conditional on the presence and/or consent of the parent, legal guardian, or legal-age spouse.