A question about superman and thor?

Kriptonians don't speak English, they speak Kriptonian, and this has been represented in the comics, it's just hard to get a conversation across in a language that doesn't exist, especially when it applies to a story line. The Kriptonians are extremely advanced and intelligent also, so anybody not native to the Earth, or American for that matter, would pick up the languages fairly easily. Superman's father sent him to earth, and had researched the planet in depth so he likely knew English before and this was part of a failed escape plan, thus the reason why he can communicate with his son in English. Clark was raised in the US and is native English speaking, while in the comics he also knows most of Earth's languages along with many other extra terrestrial languages, including Kriptonian.

Thor on the other hand is Asguardian, which in comics is the race which influenced many polytheistic religions, mainly Norse, German, and Viking religion. The Asguardians constantly watch the Earth for threats, which is a reason they abandoned protection of Earth, they had other threats to deal with, along with potential threats from the people of Earth if they continued to influence them. They are extra-dimensional aliens which means they can probably instantaneously pick up languages just from short interactions with those intelligent species, some Asguardians can even communicate with lower life forms, Balder. He was placed on Earth as a punishment to learn humility, the reason why it was in the US is unknown.