Alright, you'll have to forgive me for the lengthy response in advance, as there are seven decks to talk through here. So with no further delay...
Captain America - I see what you did there with the red, white and blue. Champion of the Parish is great and could be a monster when combined with the other humans entering the battlefield (especially with Cathars' Crusade) - Wingcrafter making it flying would also be nice. But, I can see a number of problems with this one. First, where do your blue mana come from? Second, to the same end, does it really need the third color? I get how the name works with it being three colors, but from a playing perspective, cutting it to just two colors would work wonders. If you wanted to remove the red, Thatcher Revolt could be replaced with Timely Reinforcements that both produces human tokens that don't die at the end of the turn and it could possibly give you six life for the same cost. Then, you can replace the Zealous Conscripts with Commander's Authority and even add another Cathars' Crusade to increase the likelihood you pull one. Then at turn five, you're producing humans every turn that are pumping up your CotPs or everything else with Cathars' Crusade. I can speak from experience that combo gets nasty REALLY fast. Third, why the emphasis on flickering here? Outside of Zealous Conscript and a few other counters for CotP, you really aren't getting as much benefit as you could. I can see where some other spells, either for control or drawing, would be more effective here. Fourth, I'm not a big fan of Fling, especially when all the creatures you have are so essential to the deck's functioning. What would you fling? One of the CotPs? Why not just attack and keep him? Anything smaller wouldn't really do any major damage. If you're looking for removal, Pillar of Flame is a NICE choice - note the exiling part of it. Lastly, and this is a theme I'll hammer on, outside of Wingcrafter bonding, where is the flyer defense? Do you think that's enough?
Germans - I guess I can see where the deck name comes in, but that requires me to think of CoD Zombies... I like these sorts of decks because then there isn't any way for the opponent to block. The problem, however, is that you end up having to make them drop 60-70, which is certainly more to deal with than the 20 life you normally think about. To offer a few thoughts based on a combo I run in my discard deck, I like working Trepanation Blade with Altar of Dementia and Keening Stone. The idea is to take a swing with a creature, let Trepanation Blade do it's discarding damage. Then you sack the creature before it loses that power boost to cause your opponent to drop that many more cards. I've seen that combo result in somewhere around 10-15 cards being dropped in one fell swoop. Then the real one you need will be Keening Stone which, as I'm sure you can imagine, snowballs VERY fast. What I'm not seeing is why you have Vampire Hexmage in here? Just to remove the undying counter from the Mindcrusher? If so, why not run Power Conduit? It's a bit dated, but it would let you remove as many of those counters as you want while also pumping up the other creatures.
Nightmare 2 - I'm seeing some familiar combos here , where is Roil Elemental? I'm also not following why Sundial of the Infinite (and then Buried Ruin) are in here. While I can see where you would try to end the turn before the Geist's angel goes away, combat is technically over once the opponent's turn starts, so that's no dice. So if you can fill me in on that front, I'm curious. My suggestions would probably be self-serving here to move you more toward my Power Bill deck, so I'll stop on this one, suffice to say I'm curious how well it plays.
Screwed Up - I like the pairing of Unwinding Clock and Chalice of Life. I can see where that'd be, well, for lack of a better way to say it, a dick move. You might want to consider adding Recumbent Bliss, Martyr of Sands, and perhaps most importantly, Cradle of Vitality. Cradle is SICK as any creature with lifelink can double in size for only two mana, all while you're still gaining life. When paired with the other life gaining things you have in there, you can definitely see where you can make your creatures grow quickly. I actually won a very drawn out multiplayer game because of Cradle paired with Felidar Sovereign, as the vigilance and lifelink let me attack, keeping a blocker while gaining life and doubling the Sovereign each turn with the Cradle. I would actually suggest that you drop the Leonin Relic-Warder and Fiend Hunter for some sort of flying defense (see it came up again ) like Kemba's Skyguard and something else directed toward life gain like Soul's Attendant.
Altered Knight - Why have the red even in the deck if it's only for three cards? Why not just switch to mono-white? I'll be a stickler here too, but again, what about the opposing flyers? I see Leonin Skyhunter, but what if they remove those? Then you're up the creek, right? There are a number of white flying knights available (I'm digging Skyhunter Prowler or Skyhunter Skirmisher, or for a good laugh with your friends, Ladies' Knight ).
Spirit U/W - I know it's been done to death, but it's almost required to have Lingering Souls in here, isn't it? Shimmering Grotto already splashes in a few black to flash it back, otherwise you could just live with it coming out once and being gone (or using another card to get it back, i.e., Elixir of Immortality, which you have in the deck already). Some of those Adaptive Automatons you have in Altered Knight could work in here too. I should note that this is the first deck I've seen that has a means of combatting getting top-decked. I'm a big fan of Call to the Kindred in single creature subtype decks.
Delver - Really? C'mon man. Delver has been done to death by everyone. It might work, but I'd suggest blowing it up out of spite. If you were really going to stick to it, I would recommend centering around Runechanter's Pike and unblockable creatures like Invisible Stalker, Phantom Warrior, or even Blighted Agent. I think that would be far more amusing than just another Delver deck. But that's just my two cents.
Alrighty then, I've written about three pages here, so I'll shut up. I hope some of those suggestions help. As I'm sure you already know, playtest, playtest, playtest. Unless you're copying someone else's deck, there's no way to know if my ideas are any better than yours. Also, poor green and black feel neglected.