What are the penalties for overstaying in USA?

USA does not have exit controls, so you can go wherever you can get an airline to take you.

The airlines tell the authorities about who their passengers are, so the authorities will learn about the overstay after you have left, and it will most likely be difficult or impossible for you to enter the US afterwards.

(That is, if there is an overstay at all. The expiration date on a US visa only determines when the visa is not good for entering anymore. How long you can stay is governed by the status you got when you used the visa, and it is quite possible for that to be longer than the validity of the visa).

If CBP catches him, his next stop will definitely be India unless he can show CBP his travel to Romania is imminent. Though it's not like he's on a "wanted" poster, being caught would be a matter of dumb luck.

So if he wants to choose his next destination, he should make his own travel arrangements. The US has no exit controls, there's no routine stop at CBP to check your papers on exit, so they won't grab him then.

However I think your friend should talk to an immigration attorney about exactly what his situation actually is. The visa expiring doesn't necessarily mean overstay. Other countries may ask if he's overstayed, and he needs to have the Correct answer for that question, not an assumption or guess. He is expected to know, and if he gives an answer that is wrong, that is presumed to be lying/deception. Deception is serious business in immigration.

Keep in mind, also, that if he is refused entry to Romania (or I gather there aren't direct flights to Romania, so Heathrow*, Schiphol etc.), the carrier who brought him this far will be responsible for taking him away from that country to a country he is legally allowed to enter. That's not the USA, right?? That would be India, but if the airline in question doesn't go to India, that could be a big mess. And again, do they really have direct Romania-India flights? The intermediate airport must also be able to take you after what will now be a refusal. You may be better off choosing an airline that can definitely get you from the intermediate stop and Romania to India, and ideally does not require transit visas or immigration challenges for the transfer airport back to India. Emirates/Qatar/Etihad comes to mind.

* And Britain does require a transit visa, and they do ask if you have overstayed.

There are a few different consequences of overstaying in the US. The ones most likely to be applicable to your friend are:

• the 3-year bar, meaning that after he leaves the US, he will be banned from entering the US for 3 years following departure (with rare exceptions), and
• the "consular shopping bar", meaning that every time he applies for a US visa in the future, he must apply at a consulate in his country of nationality (India). He would not be permitted to apply in Romania.

The US generally does not intercept overstayers on their way out. We can only speculate as to why, but it seems that they would much rather have someone leave and tell them they can't come back, than to pay to detain them and put them through removal proceedings just to accomplish a similar outcome.

Whether or not these bars apply to your friend depends on details of his situation. The expiration of the visa does not mean he has overstayed. Relevant details include when his I-94 expired, whether any period of his employment was "unauthorized", whether he had ever filed to change or extend his status, and others. If he cares about ever entering the US again, he should consult an immigration lawyer as soon as possible to obtain advice about his particular situation.