That depression was caused by the terms of the Treaty of Versailles, which required reparations from Germany to all other countries.
While the US wasn't a signatory to the treaty, America pushed for Article 231, the "war guilt" article that required reparations.
And of course, the US was only involved in the war because Woodrow Wilson plunged us into it after promising to not get involved. Even before the declaration of war, America was illegally (as a neutral nation) supplying arms to UK.
Wilson got us into WWI; WWI caused WWII; WWII caused our state of "Forever Wars" that has existed ever since, all without any declaration of war.