In the end the US can't do much because they know that Iran would retaliate with force and we all know that Trump doesn't have the balls for a real war. He just wants to look tough without engaging but Iran has already called his bluff.
Keep in mind this is a short term exchange and no matter what Venezuela could always turn to China for help in rebuilding its industry. Iran probably just offered them a more lucrative deal, that's all.
Also another issue is that aside from the trouble this would cause for Trump, it would also encourage Iran to go ahead and beef up its navy so as to be able to escort such ships in the future. In case of a seizure, even building nuclear powered submarines wouldn't be off the table.
We are working on Venezuelan infrastructure for gasoline. It will take a while until they become self sufficient and there is risk of sabotage in their refineries.
We need to keep sending them gasoline. The risk is higher if we send monthly deliveries but it is our right to sell our gasoline and we can retaliate for any intervention and take their tankers in exchange. Retaliation is the key.
If there is any intervention on our tankers anytime, it means that Al-Assad attack has not been deterrent enough and further escalation is necessary.
If waters are not safe for Iran, it will not be safe for them.