The path to American license...

Foreign-trained physicians wanting to practice in the U.S. must seek certification from the ECFMG(Educational Commission for Foreign Medical Graduates). That includes passing two steps of the USMLE(U.S. Medical Licensing Examination). Once certified, they must complete residency training at a U.S. institution, regardless of their years of experience abroad.

Those wanting to specialize also must redo specialty training such as fellowships. 

Many come to the U.S. hoping to re-enter medical practice but find the process difficult and take whatever jobs they can to support their families.

So, is there any assistance in USA ?

yes. "Welcome Back Initiative centers".

Welcome Back Initiative:The program has nine centers nationwide that provide assistance to foreign-trained health professionals seeking credentials to work in the United States.

Boston - Bunker Hill Community College
Denver - Spring Institute for Intercultural Learning
Des Moines, Wash. - Highline Community College
New York - LaGuardia Community College
Providence, R.I. - Dorcas Place
San Antonio - Alamo Community College District
San Diego - Grossmont College
San Francisco - City College of San Francisco
Silver Spring, Md. - Montgomery County Dept. of Health and Human Services

Welcome Back centers offer help in many forms, including study groups, accelerated English-language classes, assistance navigating the steps to licensure, and financial aid for exams and study materials and Centers also link participants to volunteer opportunities at local clinics and hospitals to give them experience working in the U.S. health care system.
The program helps foreign-trained health professionals enter the U.S. health care work force through nine centers nationwide.

one more good news-Immigration bill aims to ease doctor shortage:providing additional visa waivers for foreign physicians who agree to practice medicine in rural areas and other regions with under served patient populations.

Raising the allocation of visas for professionals with advanced education, which includes those with medical degrees, to 40% from 28.6%. Eligible medical residents and physicians also would be exempt from worldwide immigration caps.