In the details, like the devil. Or more precisely, it depends how you define the denominator. There might be more firms per continental US, but fewer firms per globe. McDonalds, Coca Cola and the dreadful mental pollution oozing from Hollywood - or its clones - can now be found all around the globe, crowding out local products. Another possible denominator is specific industries, such as banking.
To be sure, I am not arguing one way or another, all I am saying that enumeration of new entrants to a particular market niche does not necessarily mean diversification. One way of answering this question, would be calculation of the concentration measure (Herfindahl's index - akin to Gini) - but longitudinal comparability would be a serious problem.
Wojtek