Suing is for spamming. Spamming is an unsolicited legitimate marketing call. Most of those calls originate in the US or are selling the products of US companies who hired them.

If appropriate laws existed, you could still put pressure on them. Something like "if your international partner sends more than X spam calls, you're responsible for them". The telco would have a choice of getting fined or dropping the interconnect / filtering that source. On the other side, the telco in Bangalore doesn't want to lose the ability to handle calls to the US, so starts monitoring itself.

If I could block all calls from Bangalore, that would be good enough for me.

This is not completely true. Especially in VoIP, there are usually 1-5 layers of FCC-licensed phone companies involved in the call. The CLEC (Bandwidth, Level 3, AT&T, Comcast, et al) sell their numbers to Class 3 ITSPs like Flowroute, SIP.US, VOIP.ms, SIPSTATION, Twilio, etc, and then frequently that service is once again sold to another vendor that might have an actual end-user using the service. Just because one company's switch says "where the call came from" does not mean anything related to the actual calling party.

Getting those records would likely require a lawyer and that would require a lot of spam calls. I'm talking about suing in small claims court which would be more likely for most people. Having a true caller ID would put a critical document directly in the citizens hands.