Are there more (mains) electrical safety incidents in the United States compared to the UK?
It seems there are catastrophes and there are incidents of leakage current that may cause issues.  I don't have any stats.

A catastrophe is an average power (MVA) transformer that blows up every month around the world due to insufficient Condition Based Monitoring. (CBM) for H2 and other pyrotechnic gases dissolved gas in the oil.

The UK uses a much higher safety current for RCD's based on the lethal current thru a hand and not for medical use. The American standard is almost 90% lower or  0.25mA max 100uA typ for GFCI ( don't quote exact values but something like this)  What every proficient EE fails to do is a representative Hipot &amp; ESD test above standards to failure using a &lt;100uA current limited Hipot on DC to 5kV to do non-destructive testing yet find the contaminant or component-based BVD of the insulation system. 

Then perform step rise voltages for ESD up to 25kV for no incident, operator intervention or functional failure as your specs require.

As far as the star and spring washers are concerned, this is due to lack of understanding of metal fatigue and gas-tight compression required to prevent oxidation for earth bond wire.   I once designed a system for Avaya Telecom from C-MAC EMS 20 yrs ago that had paint masking on the sheet metal. When asked by my former "metal-benders" ( sheet metal fab shop), if we could eliminate that I designed a method that UL and AVAYA accepted within 30 days with my test results and a sample for duplication of the test.  I used a star washer for the ring lug and two nuts that guaranteed contact between the bolt-nut threads, so the powder-coated painted steel chassis and star washers did not matter as washer was under high compression and gouged into the nuts while the nut/bolt threads in the  welded stud  ensured a gas-tight oxide-free joint &lt; 1mOhm where 100mOhm was the spec for a 10A cordset.

I suggest you increase your Test Engineering skills and improve your Qualification or DVT skills and apply these to all product designs whether they are yours or not. This includes a full environmental suite of stress tests and a DVT plan/Report that includes all Testing to and then above your regional medical safety limits. Remember to modify the Hipot Probe with a string of high R-values to prevent destruction on test failure yet trip the tester and not discharge the large uJ/mJ of capacitance into the target from Ionization or Voltage breakdown of the component or interface contaminated surface or air gap.