What I can tell you now that I've done what you dream to do: - You're not as stuck as you think you are (even without a visa). The startup scenes are more progressive in London, Berlin or Amsterdam, although not quite as much as in the SF Bay, of course. If I lost my right to be in the US, I would be amazingly disappointed, but I would simply go to one of these cities, and stop worrying about my country being far behind. I only realized this once my plan to get here was on track, so I stayed in Paris far too long, I'm afraid, but you don't have to make that mistake. - You have a decision to make about effort. Legally moving to SF with a job and legally moving to London with a job are both possible things, they just take a different amount of effort. For London, you'll have to make a little money first to make sure you can go from time to time to look for your next life, and to make the big move when the time comes. For the US, you'll have to make far more money first, come here 3 revenue-less months to look for a job, limit yourself to large companies (those that mind visas issues less), be overly patient with people who don't mind abusing your weakness, ... It took me 5 years to make it with this project, and I'm still one of the lucky ones; but I was willing to take a chance, and to keep fighting through the effort. - There's another road that is made possible by the European crisis; it's riskier, but faster: create your own startup. Work a Java dev job at the same time, but find an awesome startup idea, and work on it on your free time. Find time (and money) to come meet investors in SF (save money and time, and make sure you'll have interviews before coming). Investors in the US know that there are no serious investors in France or Italy these days, so they love to meet European entrepreneurs with nice startups, who are willing to move to SF. Once you're well-funded, getting a visa gets much easier.
Get in touch with me if you need help with anything else.