How are robocallers able to make international calls profitable? I have read that robocallers are untraceable because they are usually companies in India or the Phillipines.

I don't understand how this is possible. If I call India or the Phillipines, it is very expensive, a dollar or two per call. If the robocallers are paying this kind of money for each call, I don't see how that could be profitable, considering how many hangups they get.

Are foreign companies getting some cheap way to call into the US so that the pricing of international calls is highly asymmetric?
The short answer is yes

In general, technology today allows to transfer calls between telephone switches, over the internet, at zero cost (with only the fixed broadband cost), using SIP protocol

So one of the main reasons for international calls to cost differently between countries is the internal market structure of each country

Internal market structure includes in many cases operators interconnect costs or wholesale costs, regulated or not. It can also include taxes.

Calls to the US are extremely cheap
So in theory, one can download a SIP program and connect to any other person with a SIP program. All that is left is connecting to an international calls provider, and make calls...