I do not think that a state should be able to remove itself from the United States. In some ways, it does seem like states should have the right to remove themselves, but there are two major problems with this that make me think it is a bad idea.
First of all, it does not seem like it would be right for 51% of the people in a state (for example) to be able to force the other 49% to leave the country to which they have always belonged. It does not make sense to say that, in the name of self-determination for the majority, we take away the right of the minority to remain part of the country.
Second, it would be very difficult to allow any state to leave the Union in a way that is fair and equitable. There would be too many issues that would arise. What would happen to the Social Security and Medicare payments that all of the people in the state had made? How would the federal government go about getting back things like the costs of programs that they had run that helped that state? What would happen if that state had a military base in it?
All of these kinds of issues make it a bad idea to allow any state to leave the Union.