There is no comprehensive list of the over four million men that fought in World War 1 from the United States.   Most of the records were lost in a fire at the National Archives Personnel Records Center in 1973.  https://en.wikipedia.org/wiki/National_Personnel_Records_Center_fire.

The following Veterans Search is an ongoing project that started from a compilation of veterans from the State of Indiana.  Details have been added from the Indiana State Library from interviews of the returning veterans.  The interviews constitute the veterans' stories of the WWVets website.  There are over 5,000 veterans from other states included 170,000 veterans are listed, four and a half million records still needed.

Any veteran information is welcome.  WWVets@gmail.com

Many of the veterans of World War I also fought in the Spanish American War.  The State of Indiana published the book: Record of Indiana Volunteers in the Spanish American War 1898-1899. in 1900.

The complete book is available online from the Library of Congress: https://www.loc.gov/item/01005459/

Google Books also offers it for free to download:  https://www.google.com/books/edition/Record_of_Indiana_Volunteers_in_the_Span/JnYtAAAAYAAJ?hl=en 

The veterans listed in the book are listed here in a searchable database.

This list includes every Indiana volunteer veteran that fought in the four Infantry regiments, two light artillery batteries, one Company of Engineers, and one Company for the Signal Corps that were requested by President William McKinley.