Why and how do we allow law enforcement to completely ignore illegal immigrants?

As Americans we are immediately held accountable for breaking US law, yet illegals are discussed all the time with no emphasis on the fact that they have broken our law and should be punished.
They cannot just be left alone until our immigration laws change. One or the other. My problem is the term illegal and it’s acceptance. Our law must be respected under all circumstances. Americans are not just left alone if they break the law. Why should illegals be?