You and your co-workers are protected by the National Labor Relations Act to organize for a union. See What Are My Rights.
It is illegal for your employer to:
Directly or indirectly interfere with your rights to organize a union.
Threaten to or actually fire, lay off, discipline, harass, interrogate, discriminate in any way against pro-union employees because of their union activity.
Favor employees who do not support the union over those who do.
Deviate from company policy or take away any benefits or privileges employees already enjoy in order to discourage union activity.
Ask you questions about your union activities or whether you’ve signed a support card or petition.
Refuse to deal with the union once employees vote to be represented