Is it unusual that the US does not levy a wealth tax?

Of the 37 countries belonging to the OECD, only three currently impose a wealth tax: Switzerland, Norway and Spain. Fifteen years ago, 10 countries had a wealth tax.

Wealth taxes tax individuals' assets, including stocks, real estate, cash and material goods (which are difficult to value). These taxes entail high data-collection costs and are beset with the issue of wealthy individuals moving their assets out of the country to avoid taxation.

While only three countries employ a comprehensive wealth tax, many tax some kinds of assets. Belgium, Italy and the Netherlands levy taxes on selected assets (e.g., financial assets). More than half of OECD countries have some sort of inheritance tax which taxes the wealth of deceased individuals before it's passed on to beneficiaries.

Economist Thomas Piketty re-popularized wealth taxes as a potential solution to rising inequality.