It's clear you think the US is ruled like Russia. In the recent past, sanctions legislation against Russia has been passed by the US Congress by enormous margins, which makes it plausible that lawmakers could form a veto-proof majority in the near future as well. In other words, it’s not far-fetched to suggest that Congress could reestablish any sanctions against Trump’s will.  To be sure, Congress will chose to believe U.S intelligence services over the statements provided by a former British diplomat of dubious repute.