Thereof, which Indian mobile network works in USA?
Yes you can use your Indian SIM in the USA. India operators like Airtel and Voda have tied up with AT&T. So, you'll get AT&T's network in almost all the cities in the USA. Activate international roaming package on your current number and you're good to go.
Beside above, how do I activate Vodafone roaming in USA? For postpaid, you have to call your call center and get it activated. You may also get it activated via logging in to your account (via self-care portal or the mobile app). Some operators ask you to pay a security deposit. Check the networks with which “Prepaid Roaming” service has been launched by Airtel.
Regarding this, can Vodafone be used in USA?
Yes, in my experience Vodafone's voice and data services, even in the US, are good. You could also use Vodafone's i-Roam international roaming plans. It's free and offers unlimited data access and voice calling in 20+ countries including the USA.
Can I send SIM card from India to USA?
Can I send a SIM card from the USA to India by courier? Yes you can. Go to your local post office / USPS and ask for an EMS satchel (it's secure and cannot be tampered with). EMS is 'expedited or express mail service' - good for international small parcels and mail.