That is very untrue, just as Quaresma pointed out, it's the very fact I'm American that I've even heard of him.
Everything you say in your second paragraph however is correct, although I wouldn't say I was making a "comparison" to Dempsey and his impact, merely pointing out what he already did to the market in a timeline and suggesting that I'm not sure Green would have much immediate impact, and then following it up with me saying I'm not sure if he'll ever have that much impact for us, hence reaping the reward of investment.
Not being the best player in Bayern's academy isn't a blight against him IMO. Also, just because he doesn't look like he'll make it at Bayern doesn't mean he isn't very much fit for Spurs.
Also, apparently Spurs are apparently buying Andrija Balic for £2.5 million. I don't know who that is but it doesn't mean he's shit. Just like Green, he is a developmental player. I hope that Spurs are finally being smart and investing significantly more money in youth players. If Green ends up proving himself to be good in a couple of years we won't be able to afford him or he won't want to come here. This has happened to us over and over again with players. We need to invest in young players and trust our scouting and developmental departments to bring them along. We'll never succeed in transfer shootouts with the likes of Chelsea who have continually swiped our targets.