I'll just bring up one item that has been briefly touched upon in the thread. Every US airport I've been in has centralized security screening when going landside to airside. Many times this is for the entire terminal, although in some airports security will handle as few as a dozen gates or so. (PHX terminal 3 does this, 2 security checkpoints, one each for the 2 halves of the terminal). I have yet to see an airport in the US that uses "gate" security.

I remember a handful of airports in Europe where they did use "gate" security. If I remember correctly at TXL there was a check in counter next to the gate of your flight. You checked in, got the boarding pass and then walked through security to a rather small sterile area. If I remember correctly the sterile area I was in handled only one flight and had no food or drink options. I've also been gate cleared in AMS (for a US bound flight).

Another difference I've noticed is in the checking in process. Once again, in most US airports check in counters line a wall, often times in this pattern:

-----XXX------XXX------

Where the dashes are check in counters and the X's are security.

Airports I've been in within Europe seem to be set up a little different, with check in counters in the middle of a large floor space. The only place I've seen this setup is at IND, which is a brand new terminal. I've also seen check in setups in Europe where you check in for a specific flight, not necessarily for an airline, which I've never seen in the US.