Will these data centers still be subject to mass data collection by the us government (under arrangements similar to the prism program described in the Snowden relevations)? Does it matter at all that these centers are placed outside the us?
Just like basically this biggest nit ever, but Snowden revelations didn't reveal anything and nothing was described in them. Snowden exfiltrated a bunch of powerpoints that neither he nor you nor I can understand out of context. The most supportable conclusion you can really glean from Snowden's slide decks is the US intelligence agencies were able to intercept traffic of undersea cables.
Fiber is encrypted you know...
They weren't back then. Google had plans but they didn't start yet. They prioritised that after the leaks. Now they are encrypted.