If an individual wants to stay in the US longer than that, he or she must apply for permanent residency. People find tech jobs in the US through a number of methods. International students often secure jobs on an F-1 student visa after graduating. When that visa runs out, after a year of employment, the student may be able to have the company petition for an H-1B visa. Contact is made through email or maybe the phone.
Referrals are still one of the best ways to find a job from abroad.
Techies in the US often email friends back in India or China, referring them to the consulting companies where they work. Don't think working in the US, even if your wage will be exponentially higher, will be nirvana. In India, Sanjib Mahapatra held positions as a lead analyst and project manager, but in the US, he found things were not quite as he expected. The company that brought him to the States subcontracted him to other companies and couldn't always find work for him. Eventually, his visa was canceled.