There are a few English proficieny tests that are accepted as part of the US Immigration requirements. Keep in mind that these tests do expire and will have to be current.
1) IETLS - To pass your IELTS and be eligible for a US visa you will need to score 6.5 overall but must score a 7 on the speaking section of the IELTS exam to meet US visa standards.
3) OET - An OET Grade C+ or higher in Reading, Writing and Listening, and a Grade B or higher in Speaking will be required by Registered Nurses to show the level of English language proficiency needed for their immigration application.
Do note, that some states in the US do differ on their preferred English exam acceptance.