Yes, it is harder to implement changes in a large system than in a small system. However, you should note that Switzerland is more culturally diverse than the United States by a number of metrics, including immigration. For example, 25% of the Swiss population are foreigners, three times as much as in the US. Also, Switzerland has three official languages. Consequently, there is no national TV station or newspaper that can reach the whole country at once. But if it helps you, I'd like to mention that France also has a wealth tax and that Germany had a wealth tax until 1997.
Switzerland is vastly different from a large country like the United States. Consider just a few factors: population size, geographic area, and ethnic homogeneity. Switzerland population is 2% the size of the United States population. Its land is 0.5% the size of that of the United States. Perhaps most importantly, Switzerland is far more ethnically and culturally homogenous than the United States. The gene pool of Switzerland traces back centuries; America is a nation of immigrants. The cultural homogeneity of Switzerland removes any friction in policymaking due to cultural disagreements or economic disparity. [1]
Implementing a new policy in Switzerland is rightfully much easier than implementing one in the United States. The constraints of Switzerland allow more flexible bureaucratic structures and policymaking, with more predictable results, than the constraints of the United States.
A policy that succeeds in Switzerland, a geographically small, culturally homogenous area, may not succeed in the United States, a geographically large, culturally heterogeneous area, for any number of reasons arising from these differences. Only an irresponsible argument would compare policy success across the two countries without first acknowledging their vast differences.
[1] https://www.washingtonpost.com/news/worldviews/wp/2013/05/16...