If your goal is to teach at the university level, then I must tell you that an online PhD is not an option for you. You *must* attend the best reputed PhD program in your field that you can possibly get into, as your future employment hinges on this. And none of those programs are online. All are in person.
In most fields, there are far, far more PhD students than there are PhD level jobs. In many fields, only those graduates (and not even all of those) of the top programs end up getting tenure track positions, or even any teaching position after they graduate. If you go to a low level program, or especially one that is online, you need to know that there is a *severe* prejudice against such programs in academia. You will not gain employment, never mind a tenture track position.
I urge you to reconsider.
As for the UK/European universities – if this is true (and actually, I believe that all require at least some on-campus residency, at least at the beginning), be sure that the program is well respected in the US. The university systems in some countries are well known to be at issue. So know the rankings, and only go to respected programs.
If you want to teach at a community college level, rather than university, you can do that with a Master’s. You don’t need a PhD, except in certain fields, where it is preferred. But in business, if that’s your thing? An MBA would serve you well. And with that, I’d prefer you do an on-campus program, if there is a respected, AACSB accredited program near you. Part-time is fine.

“Ask Dr Almond”
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(see GOOGLE)