As it has been noted, 'You are entitled to your opinions but not to your facts.

Facts are hard things, particularly when they contravene one's preferred viewpoint.

There are public figures, whom i will not name here, who claim that it is not a crime to enter the country illegally. Does that mean that illegal doesn't mean illegal?

A case can of course be made that entering the country without permission should not be a crime, but that is no argument against the fact that it currently clearly is a crime.

One need only cite  Title 8, Section 1325, of the U.S. Code which defines the offense of "Improper entry by alien," which covers unlawfully entering the United States. This includes entering at a time or place other than designated by immigration officers, eluding inspection, or using false or misleading information to gain entry. Penalties range from fines and up to six months in prison for a first offense to a potential two years for subsequent offenses.  

And also,  Article IV, Section 4 of the United States Constitution, also known as the Guarantee Clause, mandates that the federal government shall guarantee each state a republican form of government and protect them from invasion and domestic violence upon request.  

Those are the facts. To alter them would require a Constitutional amendment.