Your Right to Organize
Under the National Labor Relations Act (NLRA), employees have the legal right to form a union in the workplace.
The NLRA says:
"Employees shall have the right to self-organization, to form, join, or assist labor organization, to bargain collectively through representation of their own choosing, and to engage in other concerted activites for the pupose of collective bargaining..."
"It shall be an unfair labor practive for an employer... to interfere with, restrain, or coerce employees in the exercise of the right guaranteed in section 7..."
You can and are legally entitled to the right to form a union in your workplace and an employer cannot stop you from doing just that.