Why is it important for a citizen to fulfill there obligations and responsibility

it's called being a good citizen and citizenship is important

they wanted the u.s. to fight on the side of the central powers.

powers  are  denied  to the  national governmentin three distinct ways: some  powers, such as the  power  to levy duties on exports or prohibit the freedom of religion, speech, press, or assembly, are expressly  denied  to the  national government  in the  constitution.