In addition to the issue of the potential arrest warrant, which has been extensively covered in other answers, there is another issue to consider. The UK is part of the US's Visa Waiver Program. This allows visa-free travel and requires you to complete an online form and declaration, and pay a small fee. It is the usual way for a UK citizen to travel to the US for leisure.
However, in order to be eligible, one of the requirements is that you "Must never have been convicted of, or arrested for, an offense or crime involving moral turpitude". A crime involving moral turpitude involves "conduct that is considered contrary to community standards of justice, honesty or good morals". See this excerpt from Wikipedia:
Little guidance is provided to the traveler as to which offenses are included in the definition; however the Web site of the U.S. embassy in London states that:
Travelers who have been arrested, even if the arrest did not result in a criminal conviction, those with criminal records, (the Rehabilitation of Offenders Act does not apply to U.S. visa law), certain serious communicable illnesses, those who have been refused admission into, or have been deported from, the United States, or have previously overstayed on the VWP are not eligible to travel visa free under the Visa Waiver Program.[9]
So, even if there is no outstanding arrest warrant, you will not be able to apply for the visa waiver without lying on the form. You could then be turned back at the US airport if they still have (and check) the records of your original arrest.
People who are not eligible for the visa waiver are supposed to apply for a tourism visa at the US embassy. You will be faced with the same issue there, but at least you will be more likely to be denied entry at the point of application, instead of upon arrival in the US (at which point you've already wasted your money and time).