Capital
The USA consists of 50 federal states.
The capital is Washington D.C.
Language
The national language is English.
Currency
In the USA, the US dollar (USD) is used for payment. EUR 1 is roughly equivalent to USD 1.08.
Best time to visit
It depends on what you want to do and where you want to go. For the southwest and east, the months from April to November are best. On the west coast, temperatures are most bearable between April and June. It is better not to travel to the dry states (Arizona, Utah and Nevada) between July and mid-September, as the temperatures can be unbearable. Overall, many parts of the USA have a pleasant climate, especially in spring (April to June) and fall (September to October). You can take city trips all year round.
Driving
For EU citizens, the national driver's license is sufficient. This is because Europeans can drive in the USA for up to 90 days with their driver's license. Otherwise, you will need an international driver's license. For the most part, the road network is well developed and the roads are in good condition.
Some of the traffic signs and rules may differ from those in Central Europe. The speed limits also vary from state to state. It is best to find out about the traffic rules at your destination before you travel.
As driving under the influence of alcohol can quickly land you in prison, you should only ever get behind the wheel without being under the influence of alcohol, regardless of any drink-drive limits.
Phone
If you use your home SIM card, you will have to expect high roaming charges. These vary from provider to provider. You should therefore get an American or international SIM card if the Wi-Fi in your accommodation, restaurants or public places is not enough for you. I can recommend Airalo for vacationers. If you are in America for a longer period of time, Mint Mobile offers good conditions.