The Abraham Lincoln Brigade was a loose organization of American volunteers supporting or fighting for the anti-fascist forces in the Spanish Civil War.The Lincolns are the canonical example of what I am talking about when I say it is perfectly fine for people that want to try to save the world to do so. Voluntarily, using their own lives or money.
... the brigade was made up of volunteers from all walks of American life, and from all socio-economic classes. It was the first racially integrated American fighting force, and the first to have an African-American officer, Oliver Law, led white soldiers.
American volunteers began organizing and arriving in Spain in 1936. ... By early 1937, its numbers had swelled from an initial 96 volunteers to around 450 members.
The International Brigade was used by the Loyalist army for several battles in Spain. ...
The Brigade was a cause celebre in the United States, however. Liberal and socialist groups organized fund-raising activities and supply drives to keep the Brigade afloat. News of the Brigade's high casualty rate and bravery in battle made them romantic figures to an America concerned about the rise of Fascism around the world.
But the business of the USA - the government - is as follows: "to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity". It is not to "establish our rule over others", "ensure international Tranquility", "provide for the UN's defence", or "promote the welfare of foreigners". These goals may be good goals, or maybe not. Either way, they aren't what our government is empowered to do.