In my experience with immortal, no one declares war on me until 3 or 4 of them decide to do it at once.
The City States must be allied with them as well. It isn't all of them, you can clearly see two that haven't in the screen shot.
I'm guessing you already lost, but if you survive, focus on defense and build you army. Do not lose units.
The AI will surround your 1 city with hordes of inferior units. Get an Xbow up there instead of a Musket.
Take out the Trebuchet first and foremost. They will eventually make peace, use that time to prepare for the next war.
If you have any Keshiks available, use them to plunder. Don't bother attacking and losing them.
I don't know what difficulty you're playing, but the mere fact you don't have a ranged unit in your city shows me you don't know what you're doing.
Considering your questions, I would go as far as to surmise this is your first or second game.
I played my first game at Prince, the next 3 or 4 at King, and probably 20 or so at Emperor, and now I am only playing Immortal.
Everything is built on the foundation of what you do in the early game.
Ancient Era: Rune Hunting
Classical: Expansion and early wonders
Medieval: Maximizing Religious Buildings
Renaisance: Pulling ahead of everyone else. Get to the next era ASAP to avoid wasting all your faith on useless great prophets.
(If you founded a religion. If not then you don't need to worry about this)
Industrial: Get here ASAP and with Industrialization, getting your 3 factories asap.
Every game follows this basic formula. You'll know whether you've won the game or lost by the Renaisance.
Warmongering will make nations guarded and untrusting, and more likely to denounce you, but whether they fight you is as said above, the size of your army, the crowded space of the map, and the distance of your cities to there's. Any time you start next to someone, there is going to be bad relations, it's that simple.
Attack an early neighbor who is making a lot of units, especially if they are hostile and aggressive.
The trick is to attack them BEFORE They make a large army. Don't wait for them to march over to your city with a general.
ALWAYS attack them first. It makes them play defensive. They will put their archers in their cities and won't even come out to attack your units.
Then dispose of their units without losing any of your own. Never sacrifice units unless you are trying to capture cities.
By the time they would've attacked you, they will instead be offering peace.
First thing you should captial should build are 1-3 scouts.
Make sure they become archers from ruins.
Always go to war with a city state early on, to steal a worker, and then use it or another Civ as a means to earn experience for those scout archers.
Get them promoted with either accuracy or barrage, 3 ranks, DO NOT MIX them. At level 5 and 6 get Range and Logistics.
Use these elite archers as your defense and attack instead of building catapults, and trebuchets. Those don't become useful until Artillery.
Instead of building or buying units, get military City State allies. Focus on buildings.
Stay at war with nearby civs, keep killing their units and plundering their lands.
Later on, when you are stronger, get good trade relations going. Attack guarded and hostile civs and instead of taking their trash cities, ask for gold in the peace agreement. You can get as much gold per turn as the population of the city they were offering you. Because look, if they aren't giving you a good deal in trade, then they aren't good for anything except going to war with and extorting them.
The downside is that you get warmonger penalty for starting wars, but not much.
If you intend to capture or kill cities from an early neighbor, do it ASAP before they become a threat to you and before you've met other civs.
Try to do most of your warmongering early in the game since the diplo penalities will weaken with every new era.
One capture at Extreme will get everyone to hate you.
One capture at Major will get you to early concerns with most, but clear threat with civs that hate warmongers.
Try not to exceed this limit. Pay civs to fight each other, if they are nearby and have a lot of units before they gang up on you.
Pay the AI civs to declare war on their friends. It's better if they all hate each other, rather then all being friends and hating you.
You can often buy an AI city right off the bat. Just offer them everything you have, and then declare war on them afterwards so you get it back.
Before going to war with someone, see if you can pay them to declare war on as many other entities as possible, Civs and City States.
Take advantage of cities capture in AI wars against each other. They are good targets to liberate and that will lower your warmonger rating.
If you split your army between the last city of an AI and a captured City state, and capture them both in the same turn, liberating the city state you can get away with destroying their entire civilization without any complaints from anyone.
That being said, try to avoid doing this. Try to get another Civ to destroy them so that you can liberate them and bring back into the game. That will make give you open borders, offer friendship, and vote yes for your congress resolutions.
I could go on and on, but those are some basic strategies. Do not seek to play %100 peace. Sooner or later the AI will do something deserving of war.
Declare wars to capture Great Prophets and Missionaries, so that you can buy their religious buildings or make holy sites.
