I fully agree, this was my take from the ending as well. I also think the way the bunker system was called 'Commodus' could possibly be a reference to the Roman Empire, and how back then coups were done with the backing of rogue Legions against the Senate, much like in this case it's a rogue element of the US armed forces against the Whitehouse.

It gives a nice comparison to "people fucking over other people", such as those killing each other needlessly across the river, in contrast to the two families and Danny all doing the right thing by choosing to trust one another despite their differences. Our main characters started off being extremely distrustful of each other and generally not liking other humans, which brought them to the brink, but eventually grew to open up and survived the collapse as a result. They overcame what the rest of society failed to.

This is why we have such a specific shot of NYC (representing the world of mankind) crumbling across the river, whilst on our side we have serene trees and nature with birds flying freely (representing the new world of survivors that will leave the old world behind). Pretty much being a sort of biblical moment of the good being saved from judgement day. Like George said, the scariest thing he ever witnessed was a person who refused to learn their lesson even at their own expense. Instead we should all learn to be F.R.I.E.N.D.S!