The difference is just in the type of license. English-US is for US customers and English-International is for the rest of the (English-speaking) world.
Are you from the United States? If so, how did you buy this product?
I think the only real difference between the US English and the International English is the higher price us none US customers have to pay for our software :(
I assume it detects the region from the serial number; I have the International English version of CS4 Design Premium but havent noticed any UK spelling in the menus etc. Although I think it did default to one of the European standards for colour management but you can still select the North American profile without any problem.
To add to the confusion, I think the difference is in the default dictionaries and the spellings in the interface, i.e. it presumes you want British-style spelling (as you have), and has nothing to do with licensing.
I have no clue how to change that election other than to re-install. If you can live with the funny spelling in the menus, you can set the default dictionary to US English in InDesign, and probably other apps.
With nothing open, click the text tool and set the control panel to character mode options. Change the language in the dictionary dropdown near the right end. This is also available from the character panel (which which is where you'd change it in Photoshop, it's in the prefs under Hyphenation in Illustrator -- and you may be able to reset the interface language in the Photoshop prefs, too).
As with EVERYTHING Adobe, they don't explain squat. I downloaded International version at 2.6GB for over an hour before realizing I could have just downloaded the 262MB file I needed. And to make sure they confuse you, they label them disk 1 of 2 and 2 of 2, which makes one believe you need both to make a set of installation disks. But, of course, that's not true. Also they don't explain AT ALL that the first series you download are actually the app that allows you to make downloads on the Adobe site (Akamai_NetSession_Installer.dmg) which is required to actually go back and re-do the download. I really hate Adobe, but can't live without it in the graphics business.
CS4 is 10 years old! Did you have a question or did you just want to rant?
That is true. I came here because I googled the International Verses Universal. I have CS5 and fixing to re-download it and I just talked to support because of my issue of needing it activated as I had activated it about 10 years ago but couldn't remember the email. They were able to help me, thankfully I remembered the email while chatting to support that I registered it with. I didn't even have my home address on my account so that couldn't help me. I stopped using it after being hurt really bad, had a back operation and more health problems came my way. I love the software and it might be 10 years old but I feel fortunate and glad I still have it.