On the continental expansion, Americans pushed Native Americans off their land making deals with them that favored the US more than the tribes. After that, Americans pushed their ideas to the areas being developed trying to make Native Americans abandon their own culture.
On the expansionism overseas the US returned the land to its original inhabitants, this happened in Cuba for example. This was the main difference between expansionism inside and outside the US.
The taking of Hawaii, Puerto Rico, and the Philippines was a violation of fundamental American ideals of self-government and democracy, this was actually the main argument of Anti-Imperialists. Once the US had claimed the territory they established their own rule and define role/impact in each respective country. Conquering other territories and forcing them to abide by American ideals and culture goes against the idea of American freedom.
Its a significant American event because of the rarity of a president being impeached. There have only been 2 impeached in History(3 if you count Richard Nixon but he resigned during Impeachment Trials)
He's talking about what happens when people disregard law and order, and the law is upheld by the whims of a mob, then what will happen is that people will not respect the government and that will happen sooner rather than later.
