How was american expansionism overseas similar to previous continental expansion westward, and how was it different? was the taking of hawaii, puerto rico, and the philippines really a violation of fundamental american ideals of self-government and democracy?

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.

your answer would be just capitalism.