Why date the nation's birth or origin to the Declaration of Independence and not the ratification of the Constitution?

The Declaration summarized the colonists' motivations for seeking independence. By declaring themselves an independent nation, the American colonists were able to confirm an official alliance with the Government of France and obtain French assistance in the war against Great Britain.

Explanation:

it foreshadows the theme of the paragraph and hints the topic that will be discussed in the paragraph!

in mcculloch v. maryland (1819) the supreme court ruled that congress had implied powers under the necessary and proper clause of article i, section 8 of the constitution to create the second bank of the united states and that the state of maryland lacked the power to tax the bank.

gibbons v. ogden, (1824), was a landmark decision in which the supreme court of the united states held that the power to regulate interstate commerce, granted to congress by the commerce clause of the united states constitution, encompassed the power to regulate navigation.