My gut feeling would say colonization was a net positive to Britain, but it's hard to say. It's just too big of a what-if. The US would have likely gone to France, their main rival at the time. On the other hand Britain spend a lot of resources on their US colonies, both building them and fighting France in America. Who knows what else they could have with those resources.

It's not just the US either. India was a profitable colony at the time but might turn out to be a major detriment to Britain overall, both as a source of cheap skilled labor and as a powerful nation of their own. Who knows what would have happened without the British. A lot of the borders in the Middle East are drawn by Britain as part of their WWI mandates/colonies, and the problems from how those borders were drawn spill over into Britain (yes, it's not the only problem in the Middle East by a long shot, but it's one of them).

I still think overall Britain came out ahead (just look at Hong Kong for what cultural influence can do), but it's not hard to imagine how colonization might be seen as a net negative if a few times things turned out even slightly worse.