not if you are underage.
if you are underage, you aren't really thought to have the ability to decide for yourself, as true or untrue as that belief may be.
so you would have to have an of age responsible adult with you.
Here is a website that will answer all your questions:
you cant go to any country (unless your country has an agreement with them, like the EU countries have an agreement with each other, etc), wiithout a visa... a visa is basically a document that says the country is giving you permission to enter and under what circumstances, so you can get a visa to work, or one to go to school, etc, they all have different rules and requirements.
Yes you can fly to america alone, again with a visa, but to get that visa they usually require a parent to be with you if you're under 18... I started university when I turned 17, so I flew back and forth by myself a few times...