france tgv ok to select "other EU" from USA?

That means nothing. If you say USA, it will bump you to Raileurope. I always put in "France" and some people put in "Antarctica".

Yes it is OK. You have a ticket in your hands (or at least a PDF printout from an e-mail which counts as a ticket) - end of problem.
I don't see a ticket inspector being interested in where you live. The ticket is for a specific seat on a specific train, that is all the ticket inspector is interested in. Anyway, you could have been in London, Rome, Warsaw or anywhere else when you made the booking.

P.S. You will never be denied boarding because there are no pre-boarding checks. The first check is after the train is moving.
I did once see an argument on a TGV where two people (an American and a Korean) both claimed to have the same seat. When the ticket inspector came round it turned out the American did have a ticket for the correct train and seat, but the wrong date. He was surcharged heavily for not having a ticket, and sent to another empty seat. I later heard him complaining on his phone that it would never happen in the USA, he would never have been allowed on the train with an invalid ticket :-)

If you say your ticket was "approved", do you mean you can print out the receipt? If so, you are ready to go. That print-out can be shown to the attendant on the train. He/she might ask for a passport for ID, or even the credit card used (so keep it handy) but your charge will have gone through your bank and be converted from euros to your home currency. Previously, when asked for my country for ticket delivery, I specified Antarctica. No problem, ever. It's the print-out, with that hieroglyphic seal which seems to be replacing bar codes, that matters.

thank you--that's what I thought. I have a ticket locator number and the receipts with seat numbers printed on paper with the weird smartphone square (but am not taking a smartphone with due to data charges, etc.). It also says that that I can reprint at the station. I don't have A4 paper. Does A4 matter? I will be near the TGV station for several days before travel, so it's no big deal to reprint there on A4. That was my plan.

8 1/2 by 11 works just fine. Don't worry about A-4.

Elaine, what you call the "receipts with seat numbers printed on paper with the weird smartphone square" is the actual ticket. This is what you need to print out. The "smartphone square" is called a QR code and that is what the ticket inspector scans when he checks your ticket on the train.
Example here: http://1.bp.blogspot.com/-WlU88Lo6IY8/T0_KnEpHykI/AAAAAAAACqc/DxFIVdoveEo/s1600/2011-06-10_PMO-BOJ.png
Though ones I have had when I made the booking in English had English on as well as French. It doesn't have to be printed out exactly A4 size, so long as it is close enough that the QR code can still be read by the machine. Only the USA use inches, A4 is standard computer printer paper size, 297 x 210 mm.

A4 is standard computer printer paper size, 297 x 210 mm.

aka 8 1/4 by 11 5/8, That last 5/8 of an inch will be the time, date, file name added by your own printer.

Sam, it's a PDF file attached to the e-mail. So it prints out exactly, it is not like a web page where the browser re-formats it and adds a footer.
If A4 is slightly larger than your inch-based paper size then you may need to select "shrink to fit" to make sure nothing is chopped off, but I doubt that will be necessary. I sometimes have to do that when printing US-sized documents on normal A4 paper.

I've done it both ways and it doesn't make any difference. Printing an A4 document on 8 1/2 by 11 at full size just cuts out 5/8 inch of margin at the bottom of the page which contains a line of text indicating the software company which provided the ticketing technology, "Impression utilisant la technologie SecuTix".

i did shrink to fit, but wondered if it affected the "smart square" that the conductor scans (as it would be slightly smaller)? As I will be right at a TGV station the days prior, I'm thinking I'll just also reprint to be safe.