I have three questions:

Why does the Constitution allow the Federal Gov't to levy taxes?

How can a governor's message power affect the legislation in a State?

What do you think are some reasopns why the president was given almost unlimited military powers? What are some possible positive and negative effects resulting from the scope of the President's military power?

Try reading:
http://en.wikipedia.org/wiki/Separation_of_powers_under_the_United_States_Constitution
See if it becomes clearer.