Let's see.

In 1900, the US was

• third biggest country population wise
• Worlds largest economy
• very strong military, lagging the british in naval power perhaps
• geopolitically coming into prominence

In 2015, the US is

• third biggest country population wise
• Worlds largest economy
• very strong military, navy and airforce (that didn't exist in 1900)
• geopolitically in the center

So, modern equivalent of 1900 USA is 2015 USA.

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