We're assumuing this is the time machine version, where Mosconi drops in and has no time to "get used" to current conditions. He wouldn't be good enough to make it on the European side, but for the American side, isn't the only tactical question whether you take a prime Mosconi over 61 year old Earl Strickland?
In the early Mosconi cup days Europe would throw out some snooker players due to lack of dedicated world class 9-ball players, and the US is now in that same position of lacking world class talent in 9-ball. The exception is Europe in the early days did have a boatload of an alternate cue-sports talent (snooker) that they can plug holes with.
In this alternate universe with a prime Mosconi, I think current USA takes a chance on him and plugs a hole for the same reason you see Ronnie O'Sullivan playing in early Mosconi cups. If your best 5 9-ball players are underdogs to your opponents best 5 (Given Shane is now a Fargo underdog to Filler), you're absolutely taking a flyer on a god of another cue format.