When asked where you are from, the first thing that comes to mind for me is “I’m American.” It’s possible to say that I live in the US. The meaning of “the USA” and “the USA” is the same. My country’s full official name is the United States of America. The formalities of “US” and “United States” may seem slightly different. USA stands for more formal names. It is a question I have to ask if someone uses the word “USA” and why they bother adding “A” after it. You get a feeling of patriotism. The adjective “American” can be used as a noun. You used it incorrectly. The American flag, American cars and American history can all be spelled out. You could also say the Chinese flag or British cars. Nearly. need to use the adjective “American,” because in English there isn’t any good adjective for “United States.” It is not possible to say the words “United Statesian” and “US-ian”. The only form of adjectival expression you’ll find in dictionaries is “American”. It is common to use the term “America” when referring to our nation, especially when being patriotic and reverent. If you’re merely stating an unmotional fact, it is best to avoid using the term “America”. Both “America” (or “American”) are problematic. We see “America” as a shorthand for “United States of America.” However, “the Americas” means “North America and South America” and “America,” can both mean the exact same thing. People in other parts of the Americas (I believe Chile and Argentina, in particular) regard themselves and all people within the Americas as American. They dislike the term “America” being used. People use “US-ian” in Internet forums that have international members. They know it annoys certain readers to say “American”.🔥 
Karl had a great answer. According to me, the term “American” refers to a common, informal way of saying that someone is either American or, in more specific terms, American citizen. Someone who says “he’s American”, automatically assumes that he is an American citizen. Not Canadian or Mexican. If you tell someone that I’m from the USA, or USA, it does not necessarily mean citizenship. That’s the main difference for me. It’s possible to be an alien resident and claim you are American. This just means that you are a resident alien and can still claim to be from the US. Karl also said that you should not forget to include the “the” in US and USA. Genevie Shedrick (Wroclaw, Poland), last edited 44 days ago 
USA and UK are different countries. USA is the country that’s most commonly known. It has a Federal and Constitutional republic government. The United Kingdom (United Kingdom), however, maintains the constitutional monarchy/parliament governance. The head of state and representatives in this instance are elected by the citizens. These officials fulfill their duties as representatives of the government under the rules set by an established constitution. The monarch of the UK, on the other hand, is the absolute head and head state in the UK. power is not vested unto this monarch because there is usually a duly elected separate Head of government exercising political power. As in the US these leaders are responsible for enforcing a set laws, which is called a Constitution. Marquice Knott added an amendment on January 18, 2020 
USA is also known as United States of America or America. country located in North America. The federal republic consists of fifty states and one federal district. All 50 of these states as well as Washington D.C. are found on the main island. They run from east to west. Alaska lies in the northwest part of North America. It is just after Canada. Hawaii is an archipelago located at the Pacific Ocean’s middle. Five populated territory and nine unpopulated are also found in the Pacific and Caribbean.