Trail is a marketing term for XC, essentially they are the same.
No, sorry, I have to disagree.
There are a few new genres of bike being developed and marketed, each becoming more and more specialised in terms of kit, componentry, geometry, suspension travel and so on.
Essentially a XC bike is designed for speed over roughish terrain. Nowadays you find more and more sub 10kg XC bikes, out and out racers with a head down-arse up geometry. They will typically have light alloy or carbon frames, and will have short travel usually air sprung suspension forks, 80mm to 120mm, but most typically 100mm. Search for World Cup XC footage, watch Mountain Biking progs on satellite TV and you'll see exactly what I mean. These are featherweight machines for lycra-clad whippets, narrow flat bars with XCR drivetrains. You will also see these riders facing technical sections where they tend to fall off, carry their bikes, or a mixture of both.
Trail bikes are designed to hit UK trail centres. Technical singletrack is an absolute joy to ride, but it will quickly kill an XC bike. These trails have evolved to include ever increasing technical sections, with drop-offs, rock gardens, slabs, steps and jumps. All these things will break purist XC race bike. Which came first will be subject of debate, but the full-suss XC bike started to get longer travel, 120mm, then 140mm, then 160mm etc, as the centres got more and more adventurous, and riders wanted to ride faster and more gnarly technical stuff.
As the bikes became more robust they also developed different frame geometry. The rider position went further back, the bars widened, borrowing technology from Downhillers etc and the stem rose so that the rider was no longer perched precariously over a tight narrow front end when looking down a terrifying descent.
Trail specific bikes evolved from this, all with 120mm plus suspension, and you can see the sort of thing that was developed specifically for it in hardtail, Giant Talon, or Orange Crush, and full suss, Orange Five, and Trek Fuel being specific examples.
So, what about the current market? Manufacturers will add features to what was a compromise MTB in order to appeal to fashion, current market forces and their own target market. Many bikes are now being sold with wide bars and short high stems where the same model two years ago had 580mm bars and bar ends! Others are throwing new models into the melting pot such as GT's superb AM Fury. This looks, to all intents andpurposes to be a standard generic hardtail bike, and will sell to people who want a "mountainbike" but don't necessarily know what they are getting it for, otehr than a vague idea that they may want to commute along the towpath occasionally, when in fact they are buying an awesome value for money biggish hit trail bike with its raked front end and wide bars.
European market is different. A lot of their off road riding is done on what we would classify as green and blue routes. Widish, a bit rough, but no jumps, bumps etc. The Euro centric designs such as Cube tend to pitch their kit at this sort of thing, and you won't find wide bars on their hardtails, but you will find rack eyes! These bikes tend to favour trekking (the bridleway hiking on bikes sort of thing. ) and the whippet standard XC stuff as described in my firest paragraph.
No means exhaustive, but I hope this answers the OPs original question!