Theoretically yes but I can't see any situation where that would be a good idea.
Frankly I suspect it would be cheaper to finish the medical degree here (even with international fees) than doing an undergrad plus MD over there. Also if you stay the course here you know you will come out with your primary medical qualification - if you transfer to the US, you have no idea if you will get into med school over there after your degree. Also it's important to bear in mind that if you leave a medical degree in the UK, usually for any reason, you end being effectively blacklisted by all UK medical schools which means you won't be able to reapply to medicine here after you undergraduate degree there.
That said transferring to a different college in the US is not uncommon like here and they usually are able to assess your credit for transfer for standard bachelors programmes. However I don't know to what extent medical school credits would transfer to a baccalaureate programme there. You'd also still need to take all your gen ed classes anyway so you won't have "accelerated" your route that much going over there (if at all - it might take longer to complete the undergrad + medical school there than just finishing the course here).
Being a US citizen means you've already overcome one of the big barriers to getting a job in the US as a medic after finishing your degree here anyway. So it's not like finishing your degree here rules out going back to the US to do your residency there (you may need to do F1 here first, as I think F1 in the UK corresponds with what is the final year of medical school in a lot of other countries).