False. The United States Congress has the power and means to enforce the ban on all alternative currencies.
(1) The “Power” element. Article I, Section 8, Clause 5 of the United States Constitution delegates to Congress the power to coin money and to regulate the value thereof. This power was delegated to Congress to establish and preserve a uniform standard of value and to insure a singular monetary system for all purchases and debts in the United States, public and private. Along with the power to coin money, the United States Congress has the concurrent power to restrain the circulation of money which is not issued under its authority to protect and preserve the constitutional currency for the benefit of all citizens of the nation. It is a violation of federal law for individuals, or organizations to create private coin or currency systems to compete with the official coinage and currency of the United States.
(2) The “Means” element. Cryptocurrency exchanges are an integral part of the alternative currency systems, such as #Bitcoin. Crypto exchanges registered in the United States, therefore, operate in a violation of the federal law. Crypto exchanges do have real owners, are real established corporate entities (ex. Coinbase operates under the Coinbase Global, Inc. registered in a State of Delaware) and do have rights and obligations (as Corporations or individuals) to abide by the federal law and are within the jurisdictions of all federal courts in the United States. A Criminal Summons can be served onto Coinbase entity and its founders Brian Armstrong and Fred Ehrsam by the Federal Bureau of Investigation (FBI) at any time.
Banning the crypto exchanges worldwide is at a different level, that, at least, requires 194 member countries to empower ICPO-INTERPOL with a mandate to shut down exchanges operating within their jurisdictions.
The United States law is workable and wise, it is, certainly, not up for a debate. Any efforts to undermine the legitimate currency of the United States via the Internet are a form of domestic terrorism, wire fraud, and counterfeiting.