Did you read the Heritage report about what it will cost to legalize them and give them access to SS, Medicare, Welfare, etc.,? It's already costing us something like $ 20,000 per illegal family per year for health care, schools, etc., without legalizing them and giving them access to programs that legals can access.
It might be a "major burden" on their employers if "millions of workers" were "lifted out of the economy," but it would hardly be a "major burden to the country or economy" or the taxpayers.
Actually, I didn’t read the report. I should.