Yes.
The Tet Offensive
In World War One, which began in 1914, the US was steeped in isolationist policies as they saw no gain in involving themselves in European wars and the hardships that would entail. The oceans provided a protective barrier from German aggression, for example.New weapons, and large numbers of them, namely submarines endangered the lives of Americans and made any ocean voyage a potential for death as Germany resorted to non-restricted submarine warfare. This placed "barriers" to America. That brought the US into World War One in 1917.
Woodrow Wilson and WWI. It is when we began to want to change the world in the image of the US; Wilson's rhetoric for joining the war effort has been used in every single war since.
In the years leading up to World War II, the American military was relatively unprepared and underfunded, reflecting a strong isolationist sentiment among the public and government. The economy, meanwhile, was recovering from the Great Depression, with unemployment still high and industrial output gradually increasing due to New Deal programs. As global tensions rose in the late 1930s, military expansion began, but the U.S. was still focused on domestic recovery rather than foreign conflict. Overall, the military's readiness and economic stability were in a state of transition as the country moved towards war.
Public education was not widely available.
The main failure was the lack of support from America, which began to emerge after WWI. Though Wilson illustrated the need for the League in his 14 points, the US public was highly isolationist both before and after WWI, leading to a lack of both political and financial support for the League.
after a New Orleans newspaper in 1926 associated its use with crime.
The Mexican-American War began
Began paying off the public debt.
Neutrality; not taking sides. Some American manufacturers and other interests were supplying the Allies though, or doing more business with them than the Central Powers. Germany's targeting the Lusitania turned American public opinion against the Central Powers.
Yes, parties began holding public nominatiions in the Jacksonian era
Women began working in factories during World War II and continued to occupy the American work force after the war.