Reading stories like these really, really scares me. I'm European, and next year my wife and I will most likely move to the US together (long story short: she is a US citizen, we have decided to move, and have already applied). I'm super excited about that. I currently work as a Rails developer, have a diverse background as a Linux sysadmin and developer, and have never had problems finding (or keeping) work where I live.
What I don't have is a college education. I'm also in my mid thirties, don't really have any US contacts, nor do I know very much about the job market there. Throw in some impostor syndrome and stuff like this creates a certain level of anxiety, to put it mildly.
Start making friends in the US, now. Look for meetups, find Facebook groups, figure out which companies have a significant presence in the area where you'll be relocating. You're starting from nothing with your social network but you already have valuable skills. Get to work on the networking now and you'll set yourself up to easily find work once you land ... if not sooner.
One thing that I am definitely planning on doing is sending emails to companies of interest some months before the move and just introduce myself. You're absolutely right though: networking starts now, but it is hard when I can't be there in person and go to meetups, etc.
What I don't have is a college education. I'm also in my mid thirties, don't really have any US contacts, nor do I know very much about the job market there. Throw in some impostor syndrome and stuff like this creates a certain level of anxiety, to put it mildly.