All by itself it isn’t. Same goes to every European country.
But the EU is.
This will likely be one of the most long-term damaging impacts of Brexit. There's no way that Britain is going to be more influential in international affairs outside of the EU than within it. You could argue that such is a secondary concern to focusing on domestic issues, but a lot of the Brexit campaign seemed to revolve around sentiments about how extricating themselves from the political union and going it alone would somehow restore some of their former prestige. Instead, they needlessly burned their bridges with a neighboring politico-economic bloc which wields far more leverage than they do.
