It depends on which tax rate you are talking about and which countries you are including in the comparison.
The US does have the highest general top marginal corporate income tax rate in the OECD (a group of rich/developed countries), but worldwide it only has the third highest (after the United Arab Emirates and Puerto Rico). These can be further adjusted to use effective rather than merely nominal rates, but both of these measures are commonly used by economists and journalists, so it is unclear which one was being referred to in the speech.
On the other hand, according to Investopedia, the US has lower income tax rates than many other countries. For instance, the income tax rate for average-earning singles with no children in Belgium is 42%, 39.7% in Germany, 36.1% in Denmark, but only 25.6% in the US.