Electrical outlet fried 3 USB chargers and causes projector to shutdown.What to do?
You should only do the following if you are electrically competent. Working live is dangerous and could lead to ventricular fibrillation and death.

There are a couple of things to try. However, these are only basic checks that in all honestly will probably reveal little. A more comprehensive set of tests should be carried out but are beyond the scope of most people.

Firstly checking all the terminals are tightly connected as arcing and overheating is a possibility of loose terminations.

Check the phase to neutral, phase to earth/ground and neutral to earth/ground are correct. You seem to have done a part of that. However, earth/ground to neutral voltages are not uncommon depending on what is connected and certainly 1-2V is nothing to be worried about. 

It is highly doubtful the outlet is at fault. Most outlets are at their fundamental level mechanical electrical switches, they posse no ability to inherently damage appliances.

That being said if the socket is one of these new USB chargers that are built directly into the sockets plate then it is certainly a possibility the transformer has become faulty as this is actually quite common from experience as they are always overloaded by larger devices such as iPads.

The real cause is more likely to be one of the following but is difficult to diagnose as it requires specialist tools.

It could be electrical surges coming in through your main supply even though it is supposed to be regulated against such surges it is certainly a possibility. In these cases it tends to wipeout several appliances that are not protected against such surges but this doesn't seem to be the case here.

Do not use cheap or fake/imitation USB chargers (I cannot stress this enough). There are a thousand articles out there about them. They use cheap sub-standard electronics that produce horrible rippled direct current output and introduce harmonics back into the alternating current supply side. They also tend to overheat a lot.

While on the topic of harmonics it is actually one that not many people truly appreciate or understand yet it is a likely cause of electronics to fail.  Harmonics can come from within the property or from outside. These harmonics can be produced by other electronics and devices such as switched mode power supplies, fluorescent lighting, UPS, magnetic cored devices. Without analysing the supply you would not be able to tell other than devices overheating and prematurely failing.

In the end it is difficult to diagnose your issue over the internet without more information.