What the government is doing is repugnant, but only because most people are stupid and take the wrong lessons from it. If people had their shit together, then it would actually cause a positive effect, and we'd be talking about how US government's thuggery inadvertently did everyone a favor.
I never even heard of these encrypted email services until yesterday (except for hushmail about a decade ago but that was an even dumber beast) and the more I look into them, the more apparent it is that they sell .. well .. "snakeoil" is maybe too harsh, but I guess I'd have to say they sell the service of closing barn doors after horses escape. If I had to put it really nicely, to the point of sickening insincere sweetness, I suppose I could say they help you deploy "defense in depth" and I might be able to avoid making any gagging sounds as I did it.
Either the sender encrypts your email with your key, or they don't.
If they do it (i.e. if people do things right), then you don't need any service's special help with anything. All you want from your service are reliability, performance, and low prices -- a commodity, just like ISP's service of packet-passing.
If the sender doesn't encrypt the email with your key, then you're fucked. This is the common scenario, and the fact that people are basically fucked but still want to somehow mitigate it, is how this market emerged. Fair enough, I get it: when life hands you lemons, you make lemonaide. But you're taking it way too seriously, expecting far too much from a lossy premise. Your lemonaide is never going to be Dogfish Head 90 Minute IPA, ever, period. You should lament that, that people don't encrypt. You don't know who all read your PLAINTEXT before it got to Silent Circle or Lavabit and then they encrypted the storage of it.
(Worse, from what people are hinting about how lavabit worked, it sounds like they did the storage wrong, and that everyone always knew they would be able to decrypt things under certain circumstances, if forced.)
Users and their endpoint software must provide security. Other people's media and services running on other people's computers, can't really help you. Everything in between the endpoints is untrusted. Gag orders, CALEA-like laws, etc will make even the best-meaning services untrustworthy.
So. If it makes users feel better to move their hosting to other jurisdictions, fine. But for fuck's sake, go beyond just trying to make yourself feel better, and actually do something to make things really better: have a keysigning party. Help webmail users find and upgrade to decent (i.e. openpgp-compatible) mailreaders. And so on. Every time you see an unencrypted email come in, think about WTF went wrong and how that could have been prevented. And if you really do this, then you'll find that you can still host in America.
BTW, we've been through all this before. It's not like anything truly new is happening. All the same issues were coming up ten years ago, and ten years before that. (And probably ten years before that but I missed out on that round.) It always comes down to jurisdiction-shopping being a waste of time. You have the ultimate weapon which makes it all obsolete: 1970s PK tech. The only time you need jurisdiction-shopping is if your government outlaws the tech (France still? Not sure.).