A success by Braddock has immense consequences. For one, it entices more Indians to join with the British. Many had laid low, waiting to see which way the wind blowed. Second, it opens up the western regions to British assault. France would have to either kiss that region goodbye, or shift resources to defend it, which then leaves Quebec and Acadia vulnerable. Third, the initial failures in America lead to a change in gov't in Britain, bringing Pitt and his 'throw everything into North America' strategy, including (according to the wiki article linked) the assault on Louisbourg.
It's possible (not likely IMO), smashing victories in 1755 could lead to France accepting the loss of the Ohio Valley and pressing for peace. This would, IMO, put the kibosh on Prussia's Frederick starting the continental seven years war (my thinking being that he kicked it off at a time when France/Britain were occupied elsewhere and being aggressive in seeking continental alliances, which Britain/France thought would preserve continental peace while Frederick saw them as protection while he made what he thought would be quick, easy gains. With France/Britain at peace, the dynamics change dramatically).
With dramatic British gains, the French and Indian War likely ends much sooner. France could end it early enough to preserve the canadian portion of their empire. Or, them might lose it earlier.
