Complex sentence: In 1917, Presidents Teddy Roosevelt of the USA and Woodrow Wilson of the CSA brought their countries into WWI, as did the independent Texas--the soldiers of all three fighting together against Germany as close allies.
Split into simpler sentences: In 1917, Presidents Theodore Roosevelt of the USA and Woodrow Wilson of the CSA brought their countries into World War I, as did the independent Texas. The soldiers of all three fighting together against Germany as close allies.