While your suggestions are obviously areas where US applicants should work to adjust their strategies if applying to the UK, I think you are hugely overestimating the probability of admission.
More importantly, the students with a good chance of admission to Oxbridge typically have a very different profile to those with a good chance of admission to T20 US colleges, viz “we don’t want second rate historians who happen to play the flute” (Oxford hopefuls urged to ditch the flute and work hard - BBC News)
In addition, Cambridge at least has a definite bias against American applicants for undergrad courses, as I wrote a few years ago: Oxbridge admissions for Americans