How is isolation the most effective policy

From my point of view it is not so effective since it is like living in a neighborhood and not talking to the neighbors. You can live like that but it would be hard. Countries need other countries in today's interconnected world. In the past it proved to be a bad approach. For example, Roosvelt refused to declare war against Germany and was obliged to declare war to Japan after the susprise attack to Pearl Harbor in 1941.

here are some major conflicts i found. maybe pick one and do more research on it. (cause i ain't writing 6 paragraphs)

in 1877, the nez perce war took place.

1881 - president james garfield was assassinated.

1882 - the chinese exclusion act was passed.

1883 - a decision in the civil rights cases legalized racial segregation in the united states.

1887 - the dawes act was passed.

1893 - the panic of 1893 took place. (what a creative name)

and there are probably other topics you can find if you just search up "united states timeline," or "conflicts in the 19th century for america."

then once you find a topic you like find out how it affected the people of america and what not. (sorry if this feels a bit short changed, history was and never will be one of my strong topics)