Question 1: What is the name of this pass in German?
Tageskarte (72 Stunden = 72 hours, etc.). But, as noted, the machines can display in English.
I am not sure that ticket machines will accept most US credit cards - they've moved on to chip-and-pin cards there. You can definitely use a US credit card at a ticket counter in a major station.
Question 3: I read somewhere that this same Vienna pass can also be used in Bratislava
To the best of my knowledge, no.
However, if you go by train from Vienna to Bratislava for a day trip, you can purchase a round-trip ticket that does include local transportation in Bratislava. Ask at the ticket window in the Hauptbahnhof (the new station) for a "Bratislava Ticket" (it's called the same in German). The Bratislava ticket is cheap: €15 for both ways.