Is there any difference between "admit something" and "admit to something"?
In the case of actions, the two are interchangeable, at least in everyday conversation (possibly in formal writing it could be preferred to use "to").
But in the case of admitting facts, we can't use "to".
For example,
I admit [that] this color doesn't look good on me.
To use "to" we'd have to reword the admission to have a nominal form, such as,
I admit to this color not being my best.