Immigration is one of the primary concerns for any contractor hoping to start working in the US. Permanent employees will find it easy to get their US work permit because they’ll receive “sponsorship” for their entire stay from their prospective employer.
The US work permit, known more commonly as the B1, H1B, L1, E1 or E2 Visa, is dependent on this sponsorship because it confirms that you’ll be earning money during your stay in the country. Contracting in the US is more difficult because the work permit is tied to one employer, so you have to change it to suit each new contract. Thankfully, umbrella companies provide a convenient and effective solution to this issue.
As your permanent employer, umbrella companies are able to sponsor you for your Visa provided they’re on the register of approved sponsors. Many different companies offer this service, because it makes contracting in the US infinitely simpler and saves you the hassle of continuous paperwork. Instead of changing your work permit every time you get a new contract, you can just work how you ordinarily would under the same permit. They protect you from the bureaucratic “rain” of legal compliance with the US immigration authorities. They can even deal with the US Embassy directly.
Through their service you may be able to use a business visa to get started quickly and then transition to a work visa in the US. It depends on your specific visa requirements. Be aware you may have to register for a residence permit in the US.