Reform Federal programs that provide money to state, county, and municipal governments from grant programs to qualified expense reimbursement programs.
Rather then throw money at Blue States and Blue Cities to piss away on nonsense, like large ceramic turkeys (Brookline, Mass, expenditure of Covid funds), and illegal alien foreigners, make them submit audited requests for reimbursement to cover Federal benefits for American citizens and legal residents only.
Make all applicants for Federal benefits submit an I-9 Form, like they are supposed when applying for employment.
To stop some of the nonsense, you need to stop the supply of Federal money that underwrites and backstops that nonsense.