I think the disclosure forms aren't really an issue. The only "possible" issue is with Federal law that tries to keep foreign influence out of our elections (52 U.S. Code § 30121).
Here's a much more clear cut case where this was prosecuted... a Florida man funneled $80K from a foreign entity (Socialist Party of Albania) into Obama's re-election campaign in 2012:
Naturally, no one in Obama's campaign who TOOK this dirty money got into trouble, and this man middle man from Florida only got probation
Here's the Albanian's Socialist who funneled money to Obama in 2013 (and then became prime minister of Albania in 2013)
The judge surmised that there could be only two reasons why Kushner did not inform the FBI about the meeting when he filled out his national security application.