Well the New Republic was never seen again after the Hosnian Systems were destroyed so it seems they were wiped out by it. If the new Republic only controlled those 4 planets then there must have been some other governments or entities controlling the rest of the galaxy. 

Who knows why they were never seen or mentioned, you would think at least some of them would be opposing the first order, and surely the resistance would try to ally with them. But then we are told in TLJ the first order reigns supreme. It really makes no sense at all, they were initially a small group of extremists, then they blow up four planets and suddenly they rule the whole galaxy. No full out war or anything they just take over the whole galaxy in the space of a few hours.

But then in TROS Poe says that Palpatine's Star Destroyers are going to attack all the "free worlds"

&gt; The largest fleet the galaxy has ever known. He calls it the Final Order. In 16 hours, attacks on all free worlds begin.

So now there are other planets resisting the First Order apparently? And there must be quite a lot of them if it requires the largest fleet the galaxy has ever seen, all with death Star Lasers, to bring them in line. So where did all these "free worlds" come from when previously the First Order "Reigned Supreme"? And why did the Resistance never try to seek them out and ally with them? 

The trilogy honestly makes no sense at all, all the moves contradict each other, and often even contradict themselves. Its pointless even trying to makes sense of this mess.