You make a very good point about the relative volume, you're right that individual actions are going to overwhelm the number of international business disputes (multi-nationals tend to file in the US if they can, even if they are not headquartered here, because it's has the most well-developed legal system).

That said, number of cases still does not mean that people are litigious in the sense of resorting to lawsuits instead of other available means of dispute resolution. E.g., car collisions are a huge source of litigation. The US has 3.4x as many motor vehicle deaths per capita per year as the U.K. (and presumably, many more collisions too) because of our highly suburban structure. So if we have more motor vehicle/insurance lawsuits, it doesn't necessarily mean it's because we're quicker to rely on litigation. Employment litigation is another big one for regular people. Here in the US, if you think you were fired unfairly, there is no administrative agency that'll handle the dispute. If you think you were fired because of race you can complain to the EEOC, but either way the dispute will end up in court.