I am travelling from NYC to Paris, and returning back. If I miss my return flight to NYC, how can I book a new return flight from CDG airport?
I do not speak French, or have a laptop to reserve online.
Does some Air France counter accept cash ?
Yes you will easily find tickets from Paris to NYC, even on last minute. They might not be really cheap but you'll find some. Here are the companies offering direct flights from Paris to NYC :
And yes you can pay your tickets with cash. Just be aware that if the ticket is too expensive (more than few thousands euros), they might deny cash.
Another point, if you are transiting via Paris and you miss your connection due to delays in your flight to CDG, you are potentially entitled for an hotel room and a new ticket to NYC. There are some terms applying but keep this in mind in case of problems.
It's absolutely possible to buy a ticket at the airport, you'd have good chances of being able to find one relatively fast as Paris-NYC is a very frequently serviced route.
CDG being a big international airport, one of the busiest in Europe, you'll have no trouble finding an English speaker, if not Air France then surely an American airline. Counters will accept cash, but you'd probably need a few thousand euros at least to cover a last minute ticket like that.
Be aware that if you miss your flight, you're not entitled to anything from the airline (accommodation, rebooking) unless the flight was delayed or cancelled because of them.