A reader asked if it was okay to interview in the UK without a visa. It makes sense that countries should allow this in order to permit foreign workers to interview for a job, and the US and the UK both permit this. However, accepting any work is another question entirely, and for this your employer must sponsor your visa.
Separately, if you're going to the US and not a US citizen, but fall under the Visa Waiver Program (like the UK) you'll need a travel authorization approval (ESTA) more than 72 hours prior to departure, which the US requires to determine eligibility for the visa waiver program and for security reasons.
Both the US and the UK governments love paperwork!