North American Development Bank Improvement Act of 2019 This bill authorizes the Department of the Treasury to provide a capital increase for the North American Development Bank, a financial institution the United States and Mexico created to develop infrastructure that protect the environment along their shared border. Treasury may subscribe to and purchase 150,000 shares of the bank's capital stock, to the extent that funds are appropriated for such a purpose. Treasury shall support projects related to water pollution and conservation, waste treatment, natural gas and energy security, expanding land border crossings, and reducing pollution related to such traffic. It shall also support developing various performance measures at the bank and report to Congress about its progress imposing such measures.