So what happens if I just go to the Aldmeri Dominion and I just kill everyone there? What exactly what happen? I'm just curious and want to know. I know there's probably going to be a large bounty on my head and I'm sided with the Empire. Sorry if it sounds like a noob question.

Uh... the Summerset Isles aren't coded in the game...

I guess people would like you. Especially the nords in Skyrim and all others who loves Talos.

essential npc

EVen with 100% absorption, you still take 15% physical damage. Good luck killing a continent's worth of people.

With enough Vegetable Soups you could just keep shield bashing them to keep them off balance.

You can't go to the Aldmeri Dominion as it is not included in the game world.

I assume you mean the Thalmor Embassy. That destination is part of the main quest, and without console commands on a PC or other glitchy ways of getting in, much of it will be unreachable unless you are doing that part of the MQ that includes it and which gives you full access. If you do get to the otherwise inaccessible areas prior to entering them for the MQ, it's likely that you will end up with a bugged out MQ.

You can approach the Embassy grounds and the lock on the front gate is, as far as I know, pickable at any time... but it's unlikely that the Thalmor you can get to just by entering the grounds will be hostile unless you attack them. I went there after finishing both the CW (for the Stormcloaks) and the main quest and they still weren't hostile on sight, I had to attack them to make anything happen. They are probably programmed as non-hostile because they have to be that way when you are sent there on the MQ. If you have to attack them without provocation, I assume you will get a bounty unless you kill all of them and thus remove any witnesses.

There is also a group of Thalmor holding Northwatch Keep, farther to the west along the north coast in the same hold. You can pick up a side quest that will send you there and they will be hostile and you can wipe them out with impunity if you like.

You would be stopped at the Skyrim border by the invisible wall.

Then your a genocidal nutjob.

And that's gonna take a lot of Skooma

Summerset isle, Valenwood and Elsweyr are rather difficult to find at the momen

It would work if you played on Novice difficulty. The whole world would cheer.