It's one thing to say we beat Spain, its another to use that victory as premise to validate confidence if we were to play them again. To do that, you need to expand your perspective to more than just the score line and review the game as a whole.
Spain had enough chances in the second half to not only draw the game but to win it by a margin. When you play sides that keep the ball for the majority of the game, you need to ask yourself whether your defence can handle them. Can England's defenders be confident against Spain? I don't see how. England would need to be at their best and hope luck is on their side. To suggest that result in November act as evidence to a strength is just something beyond comprehension IMO.
A bit late back to this, but the fact that you beat someone once is always reason to believe you can do it again. You want to look at the stats? Ok, we had as many shots on target as they did. That's how you score goals. Not by passing around in front of the 18 yard box and kicking it wide once every 5 minutes.
Also, that was the strongest Spain side they could have put out. Ours was:
Hart, Glen Johnson, Lescott, Jagielka, Cole, Walcott (Downing 46), Jones (Rodwell 56), Parker (Walker 85), Milner (Adam Johnson 76), Lampard (Barry 56), Bent (Welbeck 63)
And yes, it was a friendly. But watching the game it was very clear that both sides wanted it. This isn't me saying that England will beat Spain if we plan them again. But it's not a ridiculous thing to say.