Quite a few Team USA players have better records percentage-wise than Deuel, but most of them have played only a small number of times.
If we eliminate everyone who has played in fewer than 4 Cups, we're considering just 10 players. Ranked by their winning percentages, we have:
Singles
1. Williams 6-2 (75%)
2. Archer 17-13 (57%)
3. Morris 10-8 (56%)
T4. Strickland 14-12 (54%)
T4. Deuel 7-6 (54%)
Doubles
1. Strickland 24-12 (67%)
2. Archer 27-23 (54%)
3. Jones 10-9 (53%)
4. Deuel 13-12 (52%)
Singles and doubles combined
1. Strickland 38-24 (61%)
2. Williams 12-9 (57%)
3. Archer 44-36 (55%)
4. Deuel 20-18 (53%)
All matches combined -- singles, doubles, trebles, teams
1. Strickland 43-26 (62%)
2. Deuel 27-20 (57.4%)
3. Williams 12-9 (57.1%)
4. Archer 50-41 (55%)
The above numbers count a full win or loss for each player in each match. Another way of looking at the records is to count a full point for each player in a singles win or loss, a half a point for each player in a doubles win or loss, a third of a point for each player in a trebles (played only in 2006) win or loss, and one-fifth of a point (one-sixth in 2006 when the teams had 6 players) for each player in a team win or loss. On this basis, and looking only at all matches combined, we have:
1. Williams 9.0-5.5 (62%)
2. Strickland 27.2-18.4 (60%)
3. Archer 31.8-25.6 (55.4%)
4. Deuel 15.1-12.4 (54.9%)
The career records of everyone who has ever played in the Mosconi Cup can be found here:
https://forums.azbilliards.com/showthread.php?t=464772