Yes, a national health care plan would be unconstitutional if it violated the thirteenth amendment to the constitution. The thirteenth amendment is called the slavery amendment because it was the constitutional amendment that outlawed slavery. If the government says that you are a slave, and says you are owned by an insurance company, then, yes, the health insurance plan is illegal. The thirteenth amendment not only outlaws slavery, it also outlaws servitude. Let me take a moment to explain the difference between slavery and servitude.
Servitude is a state of oppression in which you lose part of your freedom. Slavery is a state of oppression in which you lose all your freedom. Although servitude is an extremely serious crime, it is not as serious as slavery. Servitude involves only a partial loss of freedom, while slavery involves a complete and total loss of freedom. In you are held in servitude, your freedom may be temporarily taken away from you. Slavery is much worse, if you are held in slavery, you freedom is permanently taken away from you.
To determine if you are experiencing slavery or freedom, you have to ask yourself one simple question, you must ask, do I have a choice? Am I free to say ‘No, I don’t want to buy health insurance’, or has your master made that decision for you? If this was a free country, where the constitution had effectively protected your freedom, you would be free to say, “No! I Do not want to buy any health insurance! I want to live my life without paying one cent to the insurance companies! I do not want any insurance at all!” But, you are not free to avoid the insurance requirement that the federal government is imposing on you. You are are being forced to buy it. Your master, whose name is Barack Hussein Obama, wants you to buy the insurance, and so the government passed a law that says all Americans must have health insurance. So, essentially, you are the slave and Obama is the master. This is an obvious violation of the thirteenth amendment to the United States constitution.
Incidentally, there is an internnational law that also outlaws slavery and servitude. In 1948, the United Nations made the Universal Declaration of Human Rights. The U.N. Human Rights Declaration of December 10,1948 says that slavery and servitude in all their forms shall be prohibited.