You may also wish to compare the funding situation for the various advisors. Each country and university has access to different grants and other sources of funding. You have to keep in mind that doing a PhD is a
full-time job. You won't be able to have a part-time job and do quality research, so unless you are able to self-fund, the money aspect is critical.
I believe that, in general, PhDs take longer to complete in the USA, especially with the top universities. And of course, the cost of living varies with different cities.
When you write "potential advisors", have you actually engaged in communication with them? Typically principal researchers have a clearly defined programme, often tied to specific grants, funding contracts. They will only take on advisees whose proposed work dovetails into their group's work. In my experience it is very difficult to be accepted when you propose specific research and it is outside any existing scope.
To better understand the "potential advisors'" situation, I recommend that you locate recent papers by them, read those papers and compare their current and recent work with your intended work. When you contact them, you could frame your proposal to align with their research programme.
I am not a ML expert, so I can only comment generally. I would expect that post PhD opportunities in industry would be better in the USA. However, academic opportunities might be more comparable.