One of the tipping points was when the Nazis invaded Poland and started moving in on other countries. We sent troops out to the Europe area to help stop the Nazis and push them back into Germany. Another time when we couldn't avoid getting involved was when Japan bombed Pearl Harbor. This was because we had to defend ourselves from the bombing. This was considered another act of war, so we returned the message. The United States bombed Hiroshima as a warning for Japan to surrender. The Japanese refused so we bombed another one of their cities. They still refused and we were getting ready to make another bomb when they finally unconditionally surrendered. From there, we took their armed forces and guns. We protected them and signed a peace treaty. The tipping point at which the United States could no longer be considered an isolated nation was when we got involved with World War Two in 1940.
Explanation:
I have had a question similar to this, so If I'm wrong, I'm very sorry. This question may be asking about a different time when the UNited States wasn't considered an isolated nation.
