The Rocky Mountain system stretching from Canada to New Mexico is a string of mountains running along the wester United States. What factors would mostly cause this
arrangement of mountains?
Intense pressure undemeath a tectonie plate that could not breakthrough the rock

Subduction of a tectonic plate, which pushed up a neighboring plate into mountains

Two plates located at a diverging boundary with a third plate rising between them

Two plates that melted into molten rock, which later cooled into the shape of mountains

The arrangement of the "Rocky Mountain system" is caused by the subduction of a "tectonic plate", which pushed up a "neighboring plate" into mountains.

Explanation:

The Rocky Mountains were formed on the western side of the North American continent around 300 million years ago due to the subduction of the Pacific plate below the "North American plate".

The consistent and gradual subduction of heavier Pacific plate below the lighter "North American plate" caused the continental plate to rise substantially giving birth to the "Rocky Mountain system".