美国的情况比较复杂。
Unions
Federal law gives private sector, but not public sector, employees the right to join unions, have them negotiate with employers for wages and working conditions and take group action concerning their employment, including the right to strike. Private sector employers may not fire, discipline or lower the salaries of employees for joining a union or exercising their collective bargaining rights. Many states have granted public employees the right to join unions and collectively negotiate for certain benefits. However, in some of these states, such as New Jersey, unions do not have the right to bargain for employment subjects that are not controlled by federal or state law or that prevent the government agency from performing its duties.
http://smallbusiness.chron.com/private-sector-vs-public-sector-employee-rights-47957.html
教师罢工可以休矣:凡事都要适可而止