Even if you get something passed at General Synod, all the resolution can do is request that churches, associations, conferences, and other settings (outdoor ministries, etc.) of the United Church of Christ prayerfully consider the resolution.
Each congregation and setting has power over itself, and a relationship with other congregations and settings.
If one wanted to make all of the churches ONA, one would have to convince enough people in each congregation and setting. That percentage may vary, as each congregation and setting has its own bylaws that determine what makes a quorum, what percentage are required to adopt a statement such as ONA, etc.