Finally, what role do the union play in today's world?

The union is what kept the United states whole, rather than having a successfully seceded Confederacy where slavery would have most definitely still been a thing even today and discrimination would be much more heavily prominent. 

Meaning:

Manifest Destiny, in U.S. history, the supposed inevitability of the continued territorial expansion of the boundaries of the United States westward to the Pacific and beyond.

Impact:

With Manifest Destiny, most Americans got some chances to move, explore, and discover new places other than their usual community, and this was very beneficial in so many ways. The exploration is great for personal gain, socially, spiritually, and emotionally as well as economic improvement.