General Question on Ally/Allies

[boo609]

I was playing as the United States and the entire time I was allied to Great Britain. I declared a war to return my states against Mexico and they joined on the opposite side of me. After they joined the War it popped up saying they began to damage relations with me.

So now I'm like royally screwed and am wondering if this makes sense and is just a normal thing that happens or if I missed something

[Alex]

No, the AI is utterly stupid, or far more likely, simply unfinished. Just assume that those british snobs are still mad over that tea thing.

[ad5ian]

Originally posted by de_mint:

I was playing as the United States and the entire time I was allied to Great Britain. I declared a war to return my states against Mexico and they joined on the opposite side of me. After they joined the War it popped up saying they began to damage relations with me.

So now I'm like royally screwed and am wondering if this makes sense and is just a normal thing that happens or if I missed something

You got greedy and asked for too much. Never ask for too much at once. Conquer a province or at most two, then wait 5 years for the truce to pass, in the meanwhile take lands from another country. From what I noticed, if you're reputable nobody will bother you.
Others, especially great powers, will join wars against you if you ask for too much and gain lots of infamy. One trick is to look for 'take on debt' and get obligations. I'm always with my eyes on that so I can sway other countries to join my side if anything nasty happens. Or you can try to bankroll to get obligations, but that is not reliable. Other ways can be to conquer something that can be later be used as a sway in case you need it. Alliances and defensive pacts are also good to have although they just disappear for no clear reason, I think obligations are much better.

Late game, I played passed 1936, there's a huge thirst for oil, it's not even nearly enough and the countries that have large reserves and the population to exploit it, like Persia, have 0 development. So while taking Mexico by piece, expand in Asia and Africa, you'll need lots of oil and rubber, iron and coal once cars, phones and radios appear.