I want somebody to do something more than a photo op. Yes, Bukele is an authoritarian just like Trump. But Trump relies on a large amount of his base thinking that he's in the right. I don't believe he nor Bukele want the optics of concentration camp guards assaulting a bunch of members of the US Congress. And I don't believe that a bunch of concentration camp guards would be willing to assault them on livestream to the entire world.
Show up with bodyguards. They don't need to be armed, but be physically intimidating and insist that they're going to enter and find the Americans who are being wrongfully detained.
All the Democrats, or really anyone in opposition to Trump, have been doing is playing it safe. If nobody is willing to take risks then the fascists will never feel threatened. If they had the balls to try what I suggested, one of two things will happen. They guards could get violent and assault, arrest, or even kill some members of the US Congress. That would spark outrage in the US. The opposition to Trump would grow and there would be even more motivation to stop him from sending people to foreign gulags.
More likely, IMO, the guards would back down and the members of Congress would prove that Bukele and Trump aren't as all powerful as they want to seem. They'd also get live video inside CECOT to show the world exactly how horrendous it is.