Dear Sponsorship from Uncle:
Before we answer your question, let us understand the purpose of sponsorship, insofar as the immigration officials of any country are concerned. Their purpose is to ensure that an international student in their country can financially sustain himself or herself for the duration of studies. It does not matter to them whether that source of money is you, your family, your uncle, or a third party.
Since you intend to go to the UK and your uncle lives in the US, the UK officials are likely to require that you must have sufficient money in your account. Of course, your uncle can give you the money. Because your uncle is not residing under the jurisdiction of the UK government, a letter of sponsorship from your uncle is likely not to be sufficient. If however you were to go for studies in the US, a sponsorship letter from your uncle for the US officials would likely be deemed sufficient.
Please do keep in mind that while there are general guidelines on what is acceptable, the immigration officials examine each case individually and thoroughly. They may demand whatever they believe is required in their judgment before they issue you a student visa. Your college should be able to provide more accurate guidance, but in the end, you must deal with immigration officials and convince them that you would be able to sustain yourself financially through the duration of your stay.
Dear Mentor:
