Treason is defined quite specifically in the U.S. Constitution (Article III, Section 3): Treason against the United States shall consist only in levying war against them, or in adhering to their enemies, giving them aid and comfort. The Founders were specific because they were aware of the danger of what Oliver North was later memorably to describe as "criminalizing policy differences."
But the Founders did not mean that only armed attack constituted treason. The Supreme Court, in Cramer, quoted a definition of treason as "an act which weakens or tends to weaken the power of the [United States] . . ." Treason required an act and conscious intent; but not necessarily war.
Btw, describing illegals from Mexico as immigrants is a misuse of the word. They are invaders. They came into the USA illegally and did not follow any immigration paths. Therefore they invaded the country illegally. They have no rights in the country that they invaded. They broke a major law by doing this and are harming under and unemployed citizens and legal immigrants by directly competing with them for wages.
Do you think:
US Politicians / US corporations that condone (through inaction, talk of amnesty, etc.) the illegal invasion of the USA are guilty of treason?
US Politicians / US corporations that campaign to prevent law enforcement officials from enforcing immigration laws and obtaining the status of illegal invaders are guilty of treason?