frlmerrin
Banned
Really, what is most important to me is that the US brews much anti-British sentiment before the 1900s. So I thought it would work if the British supported the CSA like this:
1. CSA directly supported by Britain
Only if Britain goes to war with the Union which it would only do under very particular circumstances AND the Union has not surrendered within a very short period of time which is most unlikely.
2. USA gains more naval power; stronger blockade
Possible but only if the Union wins the ACW AND they don't end up at war with the British. If the go to war with the British there will be no blocade within a week and the greater part of the OTL Union Navy would have been sunk, burned or taken as prize and the rest will be trapped in a northern harbour. This is of course completely incompatible with your first requriement (1.) above.
3. Britain supports CSA through Mexico
(how? I don't know, I thought British intervention in Mexico would make it possible)
Nope, extremly remote possibility. You can have Britain take California, all of the west coast in fact but they (British govt/forces as opposed to merchants) have no reason to do anything via Mexico if the want to take the west coast they will and they can't be stopped by the Union, if they want to supply Texas they would do so directly and the Union could not stop them.
The French on the otherhand in the event of a prolonged (more than 3 month) Anglo-Union war would have much more lattitude than the did in OTL. They will almost certainly have access to British commercial shipping to move troops so they can put more armed warships into both the Gulf and Pacific if you like (and of course the Atlantic). So with a bigger force in Mexico and more ships they can take the place with ease and even southern California if they want. They might wish to support the Confederacy directly in order to ensure the Mexican Liberal Rebels have no haven in the CSA's/USA's west.
4. USA blocks all marine trade from Mexico going to anywhere.
This is incompatible with your first option. If you want the Union to BE ABLE TO blocade Mexico you need your option 2. because if the British are at war with the Union they won't have any ships to blocade the CSA never mind Mexico. In addition to this unless your USA agrees this option with the British, French and Spanish in some way then it will collapse before it starts because each of those nations individually has the force on station in the Gulf to lift any conceivable Union blockade of Mexico by Force Majeure. France and Britain also have the strength to lift it in the Pacific.
5. Mexico gets mad, declares war on USA
(for this to happen, I suppose more stability is necessary)
Because? They are not being blocaded as described in 5. and if the USA is at war with Britian or France or both they may not even have a border in common with the Union anymore.
6. longer American Civil War, <snip>
Well if you are going to have the Union go to war with the British at the same time it is probably going to be very short, say three months, the only way it will go on beyond 6 months is if the Union elects to attempt a war of attrition and ends up hurting itself far more than it needs to. In that case a war beyond the election in late 1864 and subsequent installation of a new Presidency in 1865 is extremely remote.