Some questions please

I will write the meanings I think are correct, kindly let me know if I'm right.

Public approval- the support of the public in something?

a 15-year high- mean here record?

trying to squash workers - I don't understand what is squash here

undermining health care- undermining, in other words please?

We have the power to overcome these attacks. Overcome here mean "to beat"?

Public approval of labor unions is at 62 percent, a 15-year high. That’s why powerful corporations and their enablers in government are trying to squash workers by pushing so-called “right to work” laws and undermining health care, workplace safety, and retirement protections. We have the power to overcome these attacks.