D'Estaing's fleet gets some favorable winds and arrives soon enough to prevent the evacuation of Clinton's Army at Sandy Hook in the aftermath of the Battle of Monmouth. Caught between the French and Washington, Clinton would be forced to surrender and you basically get a Northern Yorktown in 1778. The 5,000 strong garrison at Newport can then be mopped up thereafter and planning was also afoot to retake New York City. Getting two of these together would undoubtedly prove more than sufficient to get the British to come to terms.