Assalamu Alaikum Sister Abby,
Your questions are well-founded and similar to those asked by all of us, whether out loud or in our hearts.
I believe that the best way to achieve this unity - the way described in the beautiful Qur'an - is by personal example and determination.
3:114 They believe in God (as the One True God), and in the Last Day.
They advocate virtue by example, and close the doors to vice by
example, and try to lead in acts of collective good. Such are the ones
who enrich the society, increase the human potential and thus, rectify
their own ‘self’. [Saaliheen embraces all three meanings given in the last
Salaam Sister - let us all persevere in the name of Allah.