United States

Domestic flights are the practical way to cover the country's real distances -- major carriers connect virtually every sizable city, and a coast-to-coast flight takes 5-6 hours versus multiple days of driving.

A car is essential outside major city centers -- public transit is strong in New York, Chicago, Washington, D.C., Boston, and San Francisco, but largely absent in most of the rest of the country.

Amtrak's passenger rail network connects many major cities but runs far less frequently than European or Asian rail -- practical for a scenic journey (the California Zephyr, the Coast Starlight) but not a fast way to cover the country.

The United States is generally safe for travelers, though it's a large, varied country and personal safety practices that work in one city or region don't always apply nationwide. Most visitors experience nothing more serious than the ordinary precautions any major city calls for.

• Petty theft and pickpocketing are the most common issues, concentrated in crowded tourist areas and on public transit in major cities -- keep bags zipped and be aware of surroundings on subways in New York, Chicago, and other big cities.
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• Car break-ins targeting visible valuables are common at trailhead parking lots, scenic overlooks, and city tourist areas, especially in California -- never leave anything visible in a parked car.
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• Natural hazards vary sharply by region: hurricanes threaten the Gulf and Atlantic coasts (June-November), tornadoes are a real spring risk across the central "Tornado Alley" states, wildfires are a growing summer/fall threat across the West, and winter storms can strand travelers on rural highways in the north and Rockies. Check regional weather and seasonal risk before travel.
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• Wildlife safety in national parks is a real, serious consideration -- keep a legal minimum distance from bears, bison, and elk (wildlife injures more visitors in parks like Yellowstone every year than almost any other cause), and store food properly in bear country.
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• Gun laws and prevalence vary significantly by state -- while violent crime against tourists specifically is rare, it's worth being aware that firearms are more common in the US than in most countries visitors may be arriving from.
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• Emergency number: 911 works nationwide and connects to police, fire, or medical services.