As stated above European PhD are not typically the same as North American PhDs. I've never seen a respected program here that allows for part-time let alone while holding down a full-time job.
PhD is still a PhD in any continent. How academics organize their work is another question.
It is actually not. Many 3 year PhD or part time ones are not recognized for immigration or jobs in USA.
It's immigration policy, not qualitative PhD difference.
1. PhD in the USAs are 3 years too if you count like europeans do (we don't include the masters)
2. Industrial PhDs are not part time PhDs, it's a different thing.
Industrial PhDs are NOT part-time. They are full time, except instead of having to teach to get money you trade it for small industrial tasks.
American PhD students spend half of their time doing irrelevant things like taught classes and teaching work. They only do three years of actual research like everyone else.