I'm resident in the US on an L2 visa and will shortly be leaving to return to my home country (UK) after less than 2 years in the USA.

I've been employed in the USA for the past year and have paid all applicable Federal/Medicare/State taxes.

Am I entitled to any tax rebates upon departure from the USA?

Not unless you over-paid and are entitled to refunds.

The only way to know that is to prepare and file tax returns for the years in question.