Q about union membership in the US. Do you need to be working to be part of a union?
Where I am you can stay part of a union between jobs and companies have no legal right to enquire if your a member of one when starting employment.
If the same in the US and the employment market so bad, why would you not join a union before you had a job? That way you get support from day 1 (I can think of many reasons that it could be but don't know the landscape)
Note where I am, Union tend to be fairly large. E.G. we have only a few unions for the construction industry covering the whole country.