Can my UK university have my US visa cancelled?

Under US law and regulations, the US consular officer has complete discretion to revoke any nonimmigrant visa at any time, for any or no reason. (22 CFR 41.122(a))

Typically, however, a consulate will not revoke a visa unless they obtain information that indicates that you either did not qualify for the visa in the first place, or qualified for it at the time of application but no longer qualify.

If your visa is revoked, this fact will be entered in a US government computer network and will take effect immediately. The visa revocation will be shown to immigration officers and airlines will be instructed not to board you when they submit your passenger information. The consulate may attempt to notify you of the revocation by mail or phone, but this is not guaranteed. That the visa has not had a cancellation stamped on it is legally meaningless. (22 CFR 41.122(c) and (d))

I would suggest that you ask the university not to send the embassy anything, especially if you paid for the visa application yourself. You may explain to them that you plan other trips to the US.

If you would have qualified for the visa without the support of your university, it's unlikely to be revoked.

In any case, the issuing consulate can confirm the validity of your visa prior to travel. If the university insists on sending a letter to the consulate, I would suggest that you contact the consulate yourself and explain your situation.

If the university's letter is one of your primary supporting documents for the visa and if you voluntarily canceled your participation in the trip, then the University does have a valid reason to withdraw their support of your visa. While circumstances may have forced the decision to cancel, the University is still on record as your support/sponsor and should you abuse your privileges granted by the visa, that could effect future students from that university.

If your visa application was strong enough to stand on its own without the university's support, as others have suggested pre-emptively contact the consular division at the Embassy to tell them you are not going with the school but on your own at a later date.

Even if your application isn't strong enough for a visa, contact them before the school does to inform them of your change in plans. Better to have it on your record that YOU notified them first.