Note: I am American, and most states are aren’t “right-to-work” meaning you can quit at a moment’s notice, but it’s common courtesy to give 2 weeks notice.
The term "right to work" has nothing to do with employment status. It's political branding for laws that forbid mandatory union membership. It's a pretty effective union busting tool and has contributed to the decline of organized labor as a political force.
I think you're confusing it with "at will" employment.
I think it's fair to say teachers have the right to be teachers without joining a teachers' union. I don't think enforcing that right "contributes to the decline" of unions. Organizational models should be able to handle that sort of freedom to choose.
To me, the question is why unions don't innovate in their organizational models and policies so that giving employees freedom to choose is moot?
I don't think it's part of an American social contract that you would be forced to tangibly support candidates who have (by some accounts) immoral positions on abortion or immigration (to pick to polarizing issues).
Often times, especially in IT, when people are let go, it's often important for security reasons just to have them stop working immediately, and that worker is still going to get his salary.
When employees quit, it's not 3 months mandated, that's just the limit. You just work out your transition with your employer. Most job changes usually happen within just a few weeks.