Question

2.

Answer 1

There were several reasons why expansion seemed like an attractive choice to the United States. One reason could be for protection. Some Americans wanted to acquire the territory of Canada in order to protect themselves from a British invasion.

Another reason could be interest in natural resources. This is common in territories that have resources such as lumber, oil and coal.

Finally, another reason for expansion could be an interest in establishing a sphere of influence in a different region. For example, the United States might want to acquire a territory in Asia, or Latin America, in order to be able to exert some influence in the surrounding countries.

Answer 2

Access to the Pacific Ocean, it could be used as protection from invasion or used as a trade route to the Eastern Hemisphere. Just think of Alaska (and it is just one of many examples): 
Oil 
Fishing industry 
Forests for lumber 
Gold 

If Seward had not purchased Alaska from the Russians in the 1860's the cold war would have been a little more heated.