Re: STEM question
"1.) Is the energy efficiency of generating, transmitting and using electricity to power vehicles greater or less than that of transporting, carrying then combusting petroleum in a car cylinder?"
Generally, yes. An internal combustion engine is limited to below 50% efficiency by the laws of thermodynamics, and you can only get anywhere near the limit under very favourable conditions; in practice the average car is lucky to manage 20%. On the other hand, there are real, operating thermal power stations with efficiency over 60%. Even once you take into account transmission and storage losses, it's more efficient to have a big power station that can take advantage of favourable thermodynamics than to burn petrol in lots of small ones.
More importantly, efficiency isn't actually all that relevant, because it's almost impossible to compare like with like. A coal power station is much less thermally efficient than a gas one, but you can't burn coal in either a gas power station or your car. If coal is a good source of energy, then it doesn't matter how efficient you are at extracting it because your only choices are to burn it or not use it at all. At the other end, renewables like hydro and solar power can have close to infinite efficiency since the only major cost is the energy used in construction which a long enough lifespan can make negligible. As an extreme example, if we discovered some magic sci-fi source of unlimited free energy (imagine the usual vacuum energy or other dimensions or whatever), then even if we could only extract it with incredibly poor, <1% efficiency, it would still likely be better than all our current options. Merely looking at efficiency doesn't necessarily tell you all that much.
"2.) Is the environmental effect of generating electricity <> the effect of transporting and burning petrol"
It depends entirely on how you generate that electricity and what environmental factors you look at (or care about). Coal is generally pretty terrible environmentally, but at least it allows you to have a few centralised pollution sources that can be positioned away from population centres and potentially be dealt with locally (things like filtering and carbon capture, for example). Cars, on the other hand, necessarily produce their pollution in the exact places where people are breathing, and it's much harder to do anything useful to millions of small exhausts than a few big ones. And that's just when the types of pollution of relatively similar. How do you even go about comparing the effects of NOx production in cities to the effects a hydroelectric dam has on aquatic ecosystems, or potential issues millennia in the future from nuclear power?
Cars powered by ICEs will always be worse than just about anything else in certain specific ways, simply due to where they are. But comparing the overall environmental impact is very difficult because different methods of generating power cause all kinds of different problems - even burning coal, gas and petrol produce different pollutants.
"3.) Are there local environmental effects of ICE that add weight to the value of using electrical vehicles in some locations sufficient to justify changing, even if the net result may not be significantly advantageous."
Yes, very much so, as noted above. The current issues with diesel cars, including potentially banning them from city centres, is entirely down to nitrogen oxides, which are not nice to be inhaling in high concentrations but which disperse fairly quickly in the atmosphere. Smog in general is often a result of cars (both petrol and diesel) hanging about in urban areas - there would be a huge health benefit from removing all those engines, even if you produced much more pollution somewhere else instead.
But, again as above, it still depends on what you care about more. The local effects of cars tend to be more a problem for immediate human health - breathing in crap isn't particularly good for us. But the major environmental effects of many forms of power generation are much more wide-ranging and less immediately obvious. Global warming is an obvious one that many people still don't believe exists, but things like acid rain and ozone holes are just a couple of the better known and more easily and objectively measurable issues that we've caused recently. Would preventing some people from developing lung problems by using electric cars be worth it if we accidentally messed up some other part of environment in the process? That sort of direct local effect certainly needs considering in thinking about electric cars, but it doesn't really simplify the issue.
So basically, the answer to your key questions is that it's all extremely complicated, and anyone claiming to actually have an answer is either lying or simply doesn't understand the issue at all. That said, probably the biggest advantage of electric cars is that it doesn't matter where the electricity comes from - once we switch to electric, we're free to work on improving how we generate it all without having to worry about any further disruption. So it's not just a comparison of current cars with current power stations you need, but how they compare to how we might be generating power 10 or 20 years down the line. Of course, guessing how the future might pan out doesn't really help reduced the complication.