Page 8-9 of the summary:

there are regulatory and cultural constraints to adopting US business
practices in Europe. For example, removing poorly performing workers is extremely difficult
especially for longer tenured workers in larger firms. This is due to strong labour regulation
protecting workers against dismissal. These enable managers and workers to block changes
that may threaten their vested interests. Rapid promotion of very talented workers is also
problematic as young employees are often expected to go through extensive training and
unions prefer tenure based promotion systems to those based on individual performance. In
the US, change often occurs due to the entry of new firms and plants but this is difficult to
bring about while there are entry regulations protecting incumbents against the threat of new
entry.

Sounds like the differences are substantially enabled by a better business environment in the U.S.

All of these barriers should not be over-emphasised however, as US multinationals
appear to be able to do as well in the European outlets as they do back home (Starbucks,
McDonalds, etc).

Perhaps U.S. multinational performance in Europe should not be over-emphasized--the successful practices were presumably developed in the U.S. business environment.