As far as AmEng is concerned, does "trace" mean just about the same as "trail" in "break/blaze a trace", and -- if indeed it does -- can "trace" be used pretty much interchangeably in every which literal sense of "trail"?
'trace' does have a meaning similar to 'trail'. It is uncommon - probably the most famous is the Natchez Trace from Nashville to Natchez in Mississippi, set out in the early 1800s.
The implication is that a trail is more 'improved' and used than a trace. If I make a trace and others use it, it becomes a trail. The trace is more akin to the route you took than any kind of improved path.
I would not use the words interchangeably because of the rarity and this difference in meaning.
I grew up in Montana and "trace" is commonly understood here (and as I understand it in other mountainous areas of the US) to mean a newly cut trail unsuitable for vehicle travel of any kind. The terrain and/or vegetation prevent travel except by foot (or sometimes horse).
In the American South it is very common to have a street name use the work Trace in place of the more northern Trail, i.e., Ashland Trace, Wilson Trace. I believe the word traditionally refers to a Trace (or Trail) that follows along a Creek or Stream.
Mostly regional, and in the South, you're more likely to hear "trace" used as a "path", whereas in the midwest and North, invariably such woodland routes are referred to as "trails". Both terms come from the same root in Latin, "tractus", which is also the origin of "track". Interestingly, "track" could be considered yet another similar descriptive term for a footpath.
I've heard trace used to mean a trapline trail - used in Hazelton British Columbia by a man connected with the mining and fur trade.