Most US states don't have a safety inspection. [1]
The trend might even be moving away from some types of inspections.
For example, Louisiana recently did away with its annual inspection program for all non-commercial, non-school bus vehicles (except for some emissions testing in some locations due to federal clean air act). [2]
[1] https://en.wikipedia.org/wiki/Vehicle_inspection_in_the_Unit...
And in the UK you have to report every modification(including this one) to your insurer, or your insurance is null and void. The MOT(annual test) couldn't care any less about any of this or any modifications - as long as your car can pass a set of(very basic) tests, it's legal to use on the road.