Doing some family research WW1 + WW2

[Vegard T]

I went through some documents that were sent to my family in the 1980s-90s and I've found 2 family members that participated in WW1 and WW2 and now I'd like to start researching a bit:

WW1:
My great granduncle
Kornelius Tvedt
Lived in Iowa, participated in the First World War.
Died 29 November 1918(25 years old) from the Spanish flu one day before he was discharged from the army.
Buried in Camp Dodge, Iowa

WWI is not my main interest, so I have no idea where to start(Tried google, turned up blank).

WW2:
My great granduncle's son
Curtis Tvedt
From Iowa
All the information that is given is that he died in World War 2 and is buried in a military graveyard in Iowa
He was married(Might have changed his name? But no mention of a name change).

I've tried google and NARA, but also turned up blank.

Is it possible for me to request service records?

I could really use some help with this, since I have no idea where to start.

[Vegard T]

I got a lot of help over at us militaria forum, mostly about my relative Curtis E Twedt. But not a lot about Kornelius Tvedt, if anyone can help me find more info on him, I am very grateful.