Would you describe affirmative action as allowing anyone to join without preference to race?
Yes. That’s precisely what it is.
No it isn't.
https://en.wikipedia.org/wiki/Affirmative_action_in_the_United_States
focus on access to education and employment, granting special consideration to historically excluded groups, specifically racial minorities or women.
https://www.investopedia.com/terms/a/affirmative-action.asp
Affirmative action is a policy in which an individual's color, race, sex, religion or national origin are taken into account to increase opportunities provided to an underrepresented part of society.
https://www.lexico.com/en/definition/affirmative_action
the practice or policy of favoring individuals belonging to groups known to have been discriminated against previously.