In order to come to the United States as an immigrant, a foreign citizen must be eligible for a small handful of possible immigrant visas and for most foreign citizens, immigrating to the United States in not possible with such limitations.
The United States should allow US Citizens and Lawful permanent residents to sponsor foreign citizens for immigrant visas, as long as a documented relationship exists with that person. This means a lawful US resident can sponsor their aunts and cousins or their friends.
As the system currently works, in order to immigrate to the US, a person can apply to an immigration lottery, be a specialized worker, a student or an immediate relative of someone already in the United States.