In addition to time's post, you have a lot of irrigated tiles with no roads on them. Any time you send a worker to a tile that has no road you need to build a road. You also have several resources that have no roads to. Many of your citizens are working on tiles that have no road or any improvements whatsoever. Your capitol only has 13 shields per turn. If you mined where you haven't irrigated you can at least increase the shield output to well above 20.
You also have roads connecting your cities on the northern island but no workers. I assume you either shipped them to your main continent or you joined them to cities. You need workers on this island to build roads and improvements.
You haven't improved anything on the southern island, just built roads to connect the cities. Once again you need roads everywhere.
Some of your city placements in the New World do not make sense. You aren't going to cause a culture flip over there, in fact it's far more likely that one of your cities will flip to another civilization. The 3 cluster city near Shantung makes sense. You only need those cities to launch an attack on the continent and should have allowed the other civilizations to settle or expand into the unclaimed areas. It's not necessary to expand like that so late in the game. Let the AI finish settling their territory then conquer their cities. The time you spent shipping settlers and troops over to find those cities could have been spent elsewhere planning your invasion force.
You also have a prime settlement spot right next to your capitol, yet you haven't settled there. I retired the game to see what you did at first and some of it made sense. Yet instead of settling behind German territory you should have settled in that empty spot to reduce corruption. After that expand through war with Germany if you felt you weren't big enough.
You have Music Theory but not Chivalry? Bad. While you do have Ancient Cavalry the Knight is stronger than them. I assume you only took Music Theory for the wonder. It's actually better for you to let the AI build that wonder then conquer them later. The conquered cities will be happier and less likely to revolt or flip. It's even more beneficial if the AI who builds it is on the other continent.
You also missed Military Tradition! Cavalry will help you conquer the world so much easier. Not sure what victory condition you are going for, but either way Military Tradition and Chivalry is a must for any game - even diplomatic.
Korea has Dyes and Gems they can sell you. That's extra luxuries which will make your people happy. If you are planning to war Korea don't do the deal. If you aren't, trade them. They will want furs, wines, Music Theory, and Chemistry. Since you have such a huge tech lead giving the AI a few techs for luxuries is well worth it. Happy people are productive people.
Edit:
I think you are looking at oil and thinking it is coal. You have 2 oil as a strategic resource - not 2 coal.