European and US regulatory approval processes are very different. From what I understand, one of the bigger differences is that some EU regulatory bodies only require that a treatment be proven safe, not effective, whereas the US requires both. This means that in the EU it is sufficient to prove that your treatment is non-harmful, you are not required to prove that it actually works. In the US, you have to do both which can take much more effort.

I'm sure there are other reasons and I'm not an expert, I just had a discussion with a friend of mine that is an AIDS researcher about the drug creation process and I was interested to learn of the difference.

They've always been faster, and in fact the FDA has been catching up a bit in this regards. Waiting another few years for a cure for blindness isn't too bad. Propranolol, the first major beta-blocker, was approved in Europe in 1965 but the FDA didn't approve its use for hypertension (the most important one) until 1978. That's probably a few 10,000s of deaths right there. Though that has to be weighed against the fact that they probably saved 100s of lives by delaying their approval of practolol, a similar drug with bad side effects, so its not like the FDA's increased vigilance over Europe doesn't provide any benefit.