"now that he no longer has immunity" - any immunity that he has or had is purely a matter of power politics. Properly speaking any supposed "immunity" has never had any standing in courts outside the USA.

The same goes for any other people (with the exception of a currently reigning head of state) involved in war crimes and human rights abuses, who might be under the impression that recent legislation in the USA gives them some kind of immunity from prosecution outside the confines of the USA.

But of course power politics do come into it, and courts and judges are liable to cosy up with the people in power - so I think there's no need to worry when visiting, for example, the UK. But there are some other countries torturers and suchlike had be best advised to avoid. I'd hope Germany might be one of them.