Have collective actions better ensured American ideologies (American Dream, liberty, freedom, individualism, equality) over time?
It's a somewhat difficult problem, as the term "better" is not one that can really be measured. Also, often ideals clash. For example, extreme individualism is not really compatible with equality, and not all freedom is an unqualified good; one of the jobs of society is to prevent, for example, serial rapists and murderers from being free to indulge in their criminal activities. Society always needs to balance conflicting interests and belief systems. Collective actions, however, have been especially effective in ensuring the access of minority groups to the American Dream.
In the arena of civil rights, collective movements have both attempted to retard them and helped to develop them. Groups such as the Ku Klux Klan and the lynch mobs in the post-Civil War south attempted to limit the ability of blacks to enjoy the equal rights enshrined in the 14th amendment, luckily with only temporary success. A combination of constitutional amendment, protest movements, and legal challenges to segregation have enable blacks full de jure participation in civic life, although economic inequality persists.
Large scale collective actions have been very influential in issues related to gay rights. Both anti-gay and pro-gay collective actions have raised awareness of LBGTQ issues, and states have responded by passing both pro- and anti-gay marriage legislation. Although recent increases in legalization of gay marriage result from judicial decisions, it has been collective actions (including use of social media) that have changed attitudes to the point where gay people suffer far less discrimination than they did in the past.
For economic equality, the labor movements of the early part of the twentieth century gave workers far greater rights and freedoms and helped reduce economic inequality. Recent efforts such as the Occupy movement lacked immediate effect, but have raised public awareness to the point where economic inequality is an increasingly visible and important element of political discussions.