To be fair US president is said to be single most powerful person in the world.

I don’t have any data to back it up but I could see them being no. 1 assassination target globally.

OTOH few years back I was walking and passing near former president of my small European country. Since he is rather charismatic I asked if I can shake his hand and get a photo. He agreed and we did so, however I learned few minutes later from a friend lagging behind, that couple random bystanders twitched and totally focused on our interaction. Obviously personal security. So it’s not like security isn’t there, we might just not see it.

I’m not sure about that counter-argument. POTUS is currently the most powerful position in the world, but between 1850 and 1915 (approximate dates), I think the British and possibly French empires were more powerful.

In this time period, three American presidents were assassinated. The UK lost one MP, who was not the PM, and apparently the killers only targeted him because he happened to be walking with their main target at the time. None of the UK royals were assassinated in that period.

That may be pure luck - there were 8 attempts on Queen Victoria!

I don't know for other heads of state, but the French president has a (small) service dedicated to his protection, the Groupe de sécurité de la présidence de la République (Security Group of the President of the Republic), whose name is a little more explicit than Secret Service.

https://en.wikipedia.org/wiki/Groupe_de_s%C3%A9curit%C3%A9_d...

Fun story: at the time of its creation, in 1983, under president Mitterand, one (unofficial) mission was the protection of the illegitimate daughter of the president.