There are a lot of little things you could improve on in your 1555 AD save.
-First thing to do is secure some trades with Washington now that he's your vassal. I assume you just hadn't done this yet, but it's very important. Trade him Iron for a bunch of resources. You can get horses + rice + 3 happiness resources i think. After that trade him your techs for Chemistry so that you can work towards Steel. Cannons can win pretty much ANY Immortal game.
-You have multiple units in way too many cities. Stacking some in your capitol for the HR bonus can be good to let it grow, but there little reason to have more than 1 in most other cities. This is just costing you a bunch of gpt. The decent units should be joined with your stack. The weakest should be left behind as city guards. Any extras should be deleted if you really need money. If/when you get Cannons some of the 6-8str units could still be valuable for mop up, but you really have a lot of those right now.
-Market in Kyoto when you have +5 happy there (+8 extra Roosevelt trades) is really just not needed. I assume you are worried about your economic situation since you are negative gpt at 0% slider, but the market is only going to add 18gpt at 0%, and none at all if/when you turn the 100% research slider back on. With access to rifles i would be looking for capture and pillage gold rather than sinking big hammers into a market.
-Lots of treb production very late in the game. This only makes sense if you can upgrade them to cannons soon. You already have 11 though which is probably adequate for bombarding some defenses. I would probably stop treb production and focus on rifles.
-Crossbow in Nagoya? Why?
-Forge builds are maybe OK, but this is getting kind of late for them. Will they pay off this late? Probably, but depends how long the game lasts.
-Library in Etruscan when it already has 3 culture / turn and doesn't produce much commerce? This has clearly turned into a military game so a library that adds maybe 4 bpt doesn't make sense vs building a unit.
-IMO attacking Ragnar doesn't make sense. He's small and looking pretty harmless and if he's really Friendly with you you have nothing to worry about on that front. It's much more important to go after the big fish while you still have a tech advantage.
-It looks like you never assigned EPs to anyone. You have them split amongst everyone which means to you don't have enough on anyone to do anything useful with them. If you had focused them on Ghenghis for awhile you might be close enough to see his cities with a little bit more investment. As it stands now it would just cost a bunch of gold and quite a few turns to get to that point.
-The German log is making this kind of difficult for me, but it looks like Mongolia was fighting Korea fairly recently so my assumption would be that his stack is over there somewhere. It needs to be found a scouted. You have a lot of idle workers and those seem to be your only 2-move units so i would use a couple of those to try to scout him out quickly.
-In the mean time i would draft 3 rifles per turn, try to organize units a bit (shuffle around, delete, etc), and maybe move the bulk of your units SE towards Satsuma as it's unlikely you will want them up there where they are now.
even with a tech lead (which will surely vanish soon.
