Okay, there's one really big burning question I have on my mind. I know the answer is going to be big and complicated, as I have already read up on the subject quite a bit, with no real results. What is the big difference between American, Japanese, and to a lesser degree European parts? Also, are American parts bad, or are Japanese parts just cooler?
First off welcome to the board and I will try my best to give you my insight on this whole japanese and US parts. You could say American parts are bad but they weren't always bad. It depends on which "American" parts you buy such as HAPP or Industrias Lorenzo aka iL. iL use to make all the parts for HAPP before they got bought out by Suzo a few years back and now all HAPP parts are made in China where as iL I believe is made in Spain. Chances are if you grew up in the 90's playing SF2 in the arcades you played on sticks made by iL. Now how can you tell the difference between a HAPP or iL competition? First off deal with reputable people or vendors such as Lizardlicks that clearly sells each and doesn't try to pawn a HAPP off as a iL since iL is a bit more expensive but not by much and certainly not worth tarnishing your business reputation to make an extra dollar or two. I am going to borrow a few images from Lizardlicks so hopefully Chad won't mind and he's great to deal with by the way.
Here is a picture of a HAPP competition stick

Here is a picture of a iL competition stick

Now the reason I chose to use pictures of a blue competition stick is because HAPP's all come with black washers regardless of the color you choose whereas iL's all come color matched to the bat top. Now another difference is the color of the actuator, HAPP's are black and iL's are white. Then there is sometimes a difference with the microswitches, iL's come with usually beige cherry micro switches and have a code that say something like "D33X" or something like that and the HAPP's sometimes come with white cherry's depending where you order them from. They both are the exact same in dimension and size so you can easily interchange from one to the other. Between the HAPP and iL my preference lies with iL and there is a difference when you see them side by side in action. If I had to choose between a HAPP competition and a Sanwa JLF stick I would choose the HAPP

You can see by all my projects I am very biased towards american style parts despite them being put down as being outdated, big, bulky and not as responsive as japanese parts. Here are some pictures of the Sanwa JLF stick that is commonly found on the Madcatz Street Fighter IV Tournament Edition and the new "S" series stick that just came out last week in anticipation for the release of Super Street Fighter IV.

Then there is the optional octagonal gate which you can switch out, the one in the picture above if a square gate.

Now if you are having a hard time adjusting to your Sanwa JLF and miss the familiar feeling of a HAPP/iL competition this might be your instant fix. I've tried both gates and the square does take a bit of practice getting use to but you will also have to adjust to the shorter throws on a japanese stick as well. Also if you don't like the ball top there is a bat top add on to further pimp out your stick as well and I have tried this as well but came to the conclusion that I prefer my iL competition in the end. I will tell you one thing, this japanese stick is very noisy and gets annoying when in use and I believe there is a mod to reduce the "clickity" clicking noises.
Now buttons everyone will say that Sanwas are more responsive and I do believe this to a degree but I don't think it is night and day difference in the timing. One thing you will appreciate about japanese buttons like Sanwa is how effortless it is to push and get a signal. Some people like this but personally I don't because I found myself doubting myself and I was wrong almost 100% of the time if I pressed the button properly where as with HAPP/iL buttons I get that springy kickback once I release the button and that is how I know it registered my press properly. In the end I think it all boils down to preference and if I was to build another custom stick I would use an iL competition stick with Seimitsu buttons feel nicer then the Sanwas in my opinion. Another really nice thing is that it comes in clear so you can integrate your artwork so it doesn't interfere much like this:

One thing I will tell you about japanese parts is that they are designed to be top mounted in thin metal control panels. There are ways you could work around this such as for the JLF you replace the flat mounting plate with "S" like this so you can mount it from underneath in wood.

Another good resource on arcade parts if you haven't found it already is
www.slagcoin.comgood luck!