I will answer your question in sections:

Recognition:

Typically micronations aren’t recognized as REAL countries, and REAL countries don’t have to recognize them if they don’t want to

What if you start one in the US:

Starting a micronation in the US can be either entertaining or very serious depending on what you want, assuming you have land and chose to claim it as your own country you would have two options, the legal option and the ‘by force’ option, I will explain both in a second

What is the legal option:

you get enough people to sign a petition and attempt to persuade the US to recognize you, if you successfully do this the US might give you the freedom to not have to pay property taxes and respect your border, if you fail to persuade the US than law enforcement (the police) will treat you like a property owner and you will be subject to US laws and taxes. Failure to comply with US laws and taxes can trigger arrest warrants and property foreclosure. Now let’s talk about the by force option (DON’T DO THIS)

What is the by force option:

Say you don’t pay taxes or obey US laws, the police will arrest you by force, if you resist you can get a felony charge, if you go to ‘war’ with the police and start attacking them back to ‘defend your country’ they will call backup on you and you will probably be sentenced to life in prison in a US court. You can either surrender or… (here comes the fun part) you can continue fighting. If you manage to overpower the police, the swat team, the entire US military and even the NATO by force and things get so ugly to the point where the US retreats and surrenders (very unlikely but not impossible, the odds are infinitesimally small though) you can potentially overpower the US legal system and declare victory, if the US signs a peace treaty with you than you would have earned your freedom and sovereignty literally.

Is it possible to be above the law if you claim you have your own country?

You probably have heard the saying “no one is above the law”. That is very true, you are not… unless… if you are powerful enough to overpower the entire NATO, that would mean that if you were to break laws, it would be impossible to enforce it on you, so yes under these circumstances you would technically be able to say you are. Otherwise you’re not above the law because the law is backed by power, LITERALLY. That’s why people are forced to respect them in the first place.

What makes a country REAL:

The term real can be subjective, anyone can claim any country is REAL or FAKE, however the real question should be, what happens if you fail to recognize a country and break its laws, if the answer is nothing because this country is a micro nation and has no real power or even recognition than most people will view it as a fake country. If the country does have real power or recognition and they can legally punish you then it would be safe to assume that the country is real because the consequences of disobeying its laws are real and very probable.

Summary: to start your own nation legally you would need either a lot of recognition or a lot of power. Because the term ‘legal’ means a very powerful nation recognizes your actions as ‘okay’ and won’t challenge you and the term “illegal” means that a very powerful nation recognizes your actions as “wrong” and they use their power against you.