The patch of a U.S. Customs and Border Protection agent is shown, left, as members of the California National Guard wait next to the U.S.-Mexico border fence before a news conference on June 21, 2006. (Denis Poroy/AP)

The European Union has emerged as one of the most important supranational institutions in the world over the past few decades. This week, Britain will vote on whether to leave the institution. It's a move that could impact much of the globe — including people living in the United States.

Despite this, Americans expressing their viewpoint on the "Brexit" vote (such as, say, President Obama) have often been shouted down by those in Britain. The argument, as these Britons put it, comes down to hypocrisy: The United States would never give up its sovereignty and join a "North American Union," so it shouldn't lecture Britain on the E.U.

"The American people wouldn't stand for a court in Mexico to overrule what your courts said or … being told you can do this or you can't do that," British Parliament member Kate Hoey said in an interview with Fox News last month.

Former London mayor and pro-Brexit leader Boris Johnson wrote in one op-ed: "Is it not a blatant case of 'Do as I say, but not as I do?' "

Meanwhile, Chris Grayling, the leader of Britain's House of Commons, went further in an op-ed for The Washington Post, proposing the situation was comparable to an American Union which would include South America — and have its parliament based in Panama City.

Daniel Kelemen, a professor of political science and Jean Monnet Chair in E.U. politics at Rutgers University, suggests that this is not a useful comparison as there is no supranational political union for the United States to join. "That's just a counterfactual that stretches the imagination too far," he said.

But presumably that's the whole point? While the North American Free Trade Agreement (NAFTA), which came into force in 1994, ties Canada, Mexico and the United States together in a trilateral trade bloc, there has been no significant attempt to build upon it with a North American Union that could theoretically be compared to the E.U.

In fact, many Americans view the idea of North American political integration with a deep distrust that can verge on the conspiratorial. Relatively mainstream commentators like Lou Dobbs have suggested that trilateral meetings between the countries were a sign that America's borders were about to be destroyed, threatening to "end the United States as we know it." More extreme versions of these theories have included suggestions that a. a new transnational currency was soon to be implemented (the "amero"), b. that NAFTA will eventually create a "superhighway" between the three nations designed to abolish national borders, or c. that a North American court system would soon be implemented that would overrule domestic courts in all three countries.

These rumors are false or extremely exaggerated, but they continue to linger. They have mutated to keep up with the times: Earlier this year, fringe websites that support Donald Trump published a number of articles that suggested that Heidi Cruz, wife of former presidential candidate Sen.Ted Cruz (R-Tex.), was somehow planning to create the North American Union if her husband were elected.

Mark Fenster, a professor at the University of Florida law school who has studied American conspiracy theories, said that the fear of a North American Union is based on a "good dose of paranoid projection" but is also based on some legitimate worries. In this, Fenster said he sees some similarities with the concerns of the pro-Brexit crowd, including a fear of the loss of political control. ("The bureaucrats in Brussels are telling me what to do!" as he puts it.) Rutgers's Kelemen noted that there has been a shift in many countries to nationalist sentiments "that are tied to a distrust of things associated with experts and international associations."

There have been far-fetched proposals to further integrate North America for decades: One noteworthy example came from Technocracy, a social movement that peaked in the 1930s and had proposed putting scientists and engineers in charge of governments rather than elected politicians. However, a more realistic campaign came after the NAFTA agreement was signed in 1994 — coincidentally, the year after the E.U. was fully established.

At that time, there seemed to be plenty of people wondering if now was the time to push for greater integration in the Americas. Robert Pastor, who was a member of President Jimmy Carter's National Security Council staff, who died in 2014, was one advocate of closer integration, arguing for a "North American community" rather than a union. Pastor's ideas appear to have influenced Vicente Fox, then president of Mexico, who pushed for a North American Union in the early 2000s.

"Why can't we be not only partners in the long term, but a North American Union?" Fox wrote in a 2007 online interview with readers of The Post. "What would be better for the U.S. than having a prosperous Mexico?"

A few years later, a task force affiliated with the Council on Foreign Relations published a report that called for a "North American economic and security community" to be established by 2010. Canada, Mexico and the United States also set up the Security and Prosperity Partnership of North America (SPP) in 2005 with the aim of more cooperation on security and economic issues — much to the dismay of conspiracy theorists.

But despite this flurry of activity, the push toward greater integration now seems to be slacking — the SPP has not met since 2009, and there have been few high-profile initiatives between Canada, Mexico and the United States. Since then, J. Chappell Lawson, an associate professor of political science at the Massachusetts Institute of Technology who studies North American relations, said that it would be more appropriate to think of progress having "slowed" rather than "stalled." While there have been no "dramatic new initiatives," Lawson noted, there is "steady progress on apparently mundane issues" such as the bureaucratic problems found at shared borders.

Partly, this is simply because North American integration remains a different beast than what's happening in Europe, Lawson said.

"The projects were fundamentally different from the beginning," Lawson said. "The E.U. goal was to replace national sovereignty with a federal entity. The North American goal was to preserve national sovereignty without letting it get in the way of efficiency for no good reason."

In America at least, there's not the big need for a larger common market that a country like Belgium seeks from the E.U., Kelemen argued: The United States is already a huge country with a huge domestic market.

But why does it have that huge market? Because a number of smaller states opted to give up some of their sovereignty and federalize in the late 18th century. And ultimately, that's why the best way to put Americans in the place of Brexiteers isn't to imagine a fictional North American Union. It's to replace "Brussels" with "Washington."

More on WorldViews:

What’s a Brexit? The complete guide to Britain’s E.U. drama for confused non-Europeans.

Quiz: What do you actually know about the E.U.?

Obama’s support for the E.U. is driving some Brits mad