While Johann is a proven winner and a very highly respected instructor, there are a few reasons that this choice seems unusual, and I'm, for the moment, happy to dismiss the issue of conflict of interests --- a topic for another day.
This is surely a Matchroom choice, and suggests that Matchroom thinks that team unity and good "game day management" is all it takes to maximize performance in the Mosconi. This couldn't be further from the truth, and in my opinion, Coach Wilson provided both, though perhaps a bit less effectively than Johann can.
Europe has won seven straight Mosconi events because they are superior to the US in every category but the break:
Europe pockets balls better
Europe plays better patterns
Europe plays better position
Europe plays better safeties
Europe plays kick shots better
Europe employs more two-way shots
Europe is superior in general tactics
What it all adds up to is that out-breaking Europe by a whole lot is the only real path to victory for Team USA these days. While it's certainly possible that it could happen, it is not very likely.
Unless he's moving to the US for much of the year to work with US players, what will Johann do to narrow the gap in skills between Team USA and Team Europe and how will he accomplish it? How will he know which wild cards to pick without seeing American players up close? How will he oversee the development of the players in area of weakness?
Is this move by Matchroom just for show? On the surface, it looks pretty ridiculous, but I'll retract everything I've said if Johann will live in the US for a substantial portion of 2017 and work closely face-to-face with Mosconi hopefuls.