Presumably you have a home where you live? That's your physical office. And no you don't need a presence in every jurisdiction you serve. Visa payment network serves the world from the US.
Yes, but not where my customers live. The whole point of "sovereignty" is to serve customers from a location that is bound by the laws of _their_ jurisdiction, not mine.
It matters who can physically take control of the servers. It matters where the encryption keys are stored. The storage and processing location also matters for compliance with data residency laws.
But it's not the only thing I mentioned. Having physical offices and staff in a jurisdiction usually goes along with setting up some sort of legal and taxable entity that has personally responsible directors.
The whole issue is very complicated.