This statement is true. There are several different events that show America is far from isolationist during this roughly 160 year period. Here are some examples of major events that show America's lack of isolationism.
1) Manifest Destiny- During this era in American history (early to mid 19th century), the US gained thousands of miles in territory from countries like France (through the Louisiana Purchase) and Mexico (through the Mexican-American War and Mexican Cession).
2) Imperialism- The era of American imperialism (late 19th and early 20th century) resulted in the US expanding their territory, annexing places like Puerto Rico and Hawaii.
3) World War I (1917-1919)- The US got involved in World War I after Germany made several actions that upset the American government and citizens. This includes the sinking of the Lusitania and the Zimmerman Telegram.
Nobody else could build that canal. The Americans are the only people who could build them. They also made the Panama canal so that they could access the necessary territory.
Returning over 4,000,000 soldiers to the workforce and filling the void left by the cancellation of wartime manufacturing contracts
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Explanation:
The world war ended and there was an economic fading down because the country was involved in war time production and they have to transfer their focus to civilian and domestic production which was a major challenge. Production lines were ramped down and that led to the return of the crores of soldiers to stay unemployed for a while.
American economy was also in the verge of falling in recession due to the economic slowdown. American exports also dropped down sharply due to the war. Consumerism during the roaring twenties boosted the economy slowly and there was a gradual increase in the economic stability achieved by united states after the world war I.