We are going on a river cruise in France, but we will also visit Barcelona and take a train to Paris. It appears that a French/Spain 4 day rail pass is cheaper for 2 adults. I'm also told that it may be cheaper to purchase a point-point ticket when I get to Europe. We will travel from Avignon to Barcelona and back to Paris.
Point-to-point tickets will never get cheaper than they are now; the best rates have limited seats available. You don't need the 2- country pass; you can do this with just a France pass plus TGV reservations for the direct trains ($220 + $40 + $40 = $300 per person), which you should add at the same time you make the order, max 3 months in advance of travel, because those passholder reservations are also limited.