Hi,
I'm afraid you can't just move to the UK and work for a US company - you cannot get a Tier 2 visa to do that.
Also, you need to apply for the visa BEFORE you travel to the UK, as you cannot switch to a Tier 2 visa from a visitor visa inside the UK.
It can be extremely difficult to qualify for a Tier 2 visa, because you have to be sponsored by a UK company, for a specific job, paying a specific amount of money.... and not many people can qualify for them.
There are two ways to qualify:
1) The job with the UK company is listed on the Tier 2 Skills Shortage List, at the salary indicated
or
2) The job has passed the RLMT (Resident Labour Market Test) - basically that the UK company has advertised the job across the UK and the rest of the EU and cannot find a single suitable applicant for it, meaning they are forced to look overseas and hire you specifically. With 500 million people in the EU, unless you work in a very specified or highly-skilled field, it's unlikely you will qualify for a Tier 2 visa this way.
So, the steps are:
- find a UK company willing to hire you
- ensure that either the job is on the Tier 2 Skills Shortage List, or the company passes the RLMT
- the company then applies to sponsor you, by way of a Certificate of Sponsorship
- when the certificate of sponsorship has been issued, you can apply for the Tier 2 visa in the US (mailed to NYC)
- once you have the Tier 2 visa, you can move to the UK
- you must continue to work in that job, for the same company, or your visa will become invalid and you will have to leave