The United States is a highly industrialised nation. Health is generally not something to be concerned with while visiting the country. However, all tourists are strongly recommended to have travel health insurance upon arrival in the US as there's no universal health care and most Americans pay for private insurance, either through their employer, out of pocket, or risk having sky-rocketing health care bills in the case of medical emergencies.
The national emergency number is ‘911’ and can be dialed from any phone.
The health care system in the USA is world-class in quality, but also very expensive. Even drugs sold in the US can cost multiple times the price of the same drug in other countries.
Excellent hospitals and medical care can be found all over the US. If you do need to go to the hospital, note that the emergency room will always admit you, but you will be given a bill to pay afterwards, so keep this in mind for less-urgent issues.
Dentists are also easily found throughout the US, but once again, let them know that you are paying “out of pocket”, so you can get all fees upfront. Pharmacies can be found easily in any city and will offer medicines and other treatments for various health issues. If the issue is not urgent, it might be a good idea to go there to see what they offer.
Government-supported clinics offering free or reduced-cost testing and treatment for sexually transmitted diseases can be found in most counties and cities, but keep in mind that there is often a long wait.