[bluGill]

The US is a currency union and has been for longer. Most people forget that state originally meant the same thing as country

[jacobush]

I agree on your first point, but not the etymology. Germany has a long federal history. The word "state" has been a little ambiguous for a long time.

[dotancohen]

State was defined by political borders, country by geographical borders. For much of human history states were countries. The blurring of the meaning of these words I believe started around the 18th century as transportation, and thus the ability to rule further away, progressed.

I agree that in today's colloquial usage there is little distinction between the two.