How important is the U.S. Constitution for preserving American Liberties?

It took Vigilance to Establish and Preserve Freedom

Our freedoms, as Americans, must not be taken for granted. To do so, they will become less relevant, until they are potentially lost as a result. It's important to recognize, as the Founders stated explicitedly in the Declaration of Independence, our liberty was bestowed by our Creator, not by the good wishes of government. This truth serves as the foundation stone of our Republic.

Stated in the Declaration of Independence: "We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable rights, that among these are life, liberty and the pursuit of happiness." As further stated, "That to secure these rights, governments are instituted among men, deriving their just powers from the consent of the governed...." 

Government Control Over Healthcare.
ObamaCare, formally known as "The Patient Protection and Affordable Care Act," was passed by Congress on March 21, 2010, and signed into federal law by President Barack Obama on March 23. 

• Political analyst and commentator Dick Morris has asserted that Obama's health care plan will lead to the significant use of rationing senior health care which will decrease the life span of senior citizens.
• The centerpiece of ObamaCare is the individual mandate, a provision that makes it mandatory for every citizen to purchase private health insurance, which is unprecedented in American history. 

            Ref: http://www.conservapedia.com/ObamaCare

• Back when all Americans should have had a stake in the debate — which was when it was being written — all they got was closed door meetings and, to quote then Speaker, Nancy Peloci, “you have to pass it to find out what’s in it.”  -- Ref: http://michellemalkin.com/2011/11/16/nancy-pelosi-4/

So what's in it? We are only now starting to understand the consequences of "having to pass it to find out what's in it."  For many, the consequences are chilling, because interpretation of the law has been handed over to a bureaucrat, Department of Health and Human Services, Secretary Kathleen Sebelius, who decided that for the betterment of women 's health (from her viewpoint) -- and no matter what the Constitution may state -- Catholic entities were going to be required to pay for birth control, regardless of their religious beliefs. 
Ref: http://www.ketknbc.com/news/obamacare-it-starts

This is an obvious violation of the First Amendment of the U.S. Constitution which guarantees freedom of religion, stating: "Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof..."