Were Congress to make publishing political advertising payed for by foreign interest a crime, the tech providers would find a solution without requiring Congress to intervene in the technical details of their business. I can't imagine how such Congressional intervention would not be a horrible mess. I'm not knocking Congress here. The subject is just too far outside of scope of effective legislation.
Congress should ask Tech to face hard truth about Tech meddling in the election. Google and Facebook spent way more time and energy trying to sway voters. Russian is just an easy scape goat. If Mark Zuckerberg decides to run for president think about how scary it will be to have the full backing and support of Facebook behind him.