They are going to apply great pressure on him. They will both threaten to blacklist El Salvador in future legislation when they are back in power, and offer to funnel millions of not billions his way if he sends that guy back.
I’m betting Bukele refuses to meet with them. Give them the ultimate snub and send them back to the US in humiliating fashion.
I think POTUS has much bigger carrots and sticks than some no-name Dim Senator from Maryland