They have no cross-links, so up and down to space is going to happen multiple times in many cases. Second, they will not have data centers or ixps right where Google's ingress is, so it has to traverse fiber for quite a while. Someone gave some real numbers on the last SpaceX thread, but I believe that part alone will be 20-30ms added.

So how long until Google puts a datacenter in space?

Seeing as heat dissipation is a hard problem in space, probably never.

They do have cross-links though?

They do not have cross-links. They were in the original public announcements, but none of the current satellites have them, nor have they announced when they would be launching some that do. It's likely years away.

> Early satellites are launched without laser links, in October 2019 SpaceX expected satellites with these links to be ready by the end of 2020.

from wikipedia

That's a claim musk made, but they already have over 500 launched without them. They should have 1000 by year-end, so it's unlikely they'll be able to use them for a couple of years.