I can say maybe either trade or language. I lean more on trade because majority of native Americans didn’t speak the same language as the Europeans.
A. The US made the Gadsden Purchase.
The US never sold Texas. US won the war. Mexican cession was the US taking land.
Demeter, the Goddess of the Harvest. What happened was that Demeter wanted to get her daughter back from Hades, so she took a "resignation" from her duties as the harvest goddess and all plants were decaying on Earth, and droughts started.
B. I looked it up so I’m sorry if It is incorrect
It helped a lot with travel and trading was easy