Answer:
The economic and political expansion of the United States from the 1800s had positive repercussions both for America itself and for the world in general.
At the local level, America gradually became, from the War of 1812 to the Second World War, the main economic and political power on the planet, thus imposing its vision of the world and transmitting its ideas of freedom and opportunities to the rest of the nations. Thus, America consolidated itself in a situation of power that allowed it to have an important voice in the process of making important decisions at the global level.
In turn, the world benefited from this leadership, while the American democratic system, the recognition of freedoms and rights and the attachment to the rule of law were transmitted to the rest of the nations, thus improving the quality of life of the citizens of the world.