I am traveling from Cancun to London with a Bulgarian passport. Last year (2017) I spent 3 months traveling through the USA and my visa (B2) is valid until 4th of March.
The flight I am looking for is at the end of April and beginning of May with 2 layovers in America. Because, unfortunately, Bulgaria is not part of the Visa Waiver Program, I am traveling with a B2 instead of an ESTA.
My question is, would I be allowed to transit in the USA and if so, are they going to give me another visa?
You cannot transit the United States with an expired US visa (with the exception of automatic revalidation, which doesn't apply here). You'll need to apply for a transit visa (or another B-2 visa; you can transit on a B visa). Unfortunately, this requires paying the visa fee and an interview at a US Embassy or Consulate. You'll have to weigh whether the time and expense of getting the visa is worth any potential savings in airfare (British Airways has a direct flight CUN-LGW).
That you've been issued a visa before and, presumably, did not overstay would be a good sign that you are perhaps likely to receive another visa, but there is no way to predict that for sure.
