President Donald Trump's administration may have just fired the first shot in what could become a worldwide trade war. In response to criticisms about his announcing that the border wall with Mexico will be paid for by American taxpayers (and not, as promised, Mexico), Trump has been trying to come up with an answer for how we will be "reimbursed" by Mexico. Today, apparently, he has decided on the preferred method. The White House just announced a 20 percent tax on all imports from Mexico.

This doesn't make a whole lot of sense, but then that's never stopped Trump before. After all, a tariff of 20 percent on Mexican imports will be paid for not by "Mexico," but rather by American consumers. Cars, auto parts, food -- there's a long list of products that will become pricier for Americans to buy. The extra dollars out of American consumers' pockets (which will be necessary to buy these products) will be going to pay for that wall, plain and simple. Mexico the country -- or even Mexican companies -- will not be paying for it at all.

Will Trump's supporters even notice? That's a wide-open question. Will they buy the propaganda that "Trump's sticking it to Mexico!" or will they realize that everything now costs a couple bucks more down at Wal-Mart?

Of course, protectionism has larger goals. The tariff on Mexican imports is part and parcel of Trump's stated goal of moving factories back to the U.S. from Mexico, where they will have to hire American workers (or so the logic goes). If a company makes its products here rather than south of the border, then they won't have to pay the border tax, in other words, so they'll save enough money to pay the higher labor costs in America. Well, maybe... and then again maybe not. They might just choose to continue making products in Mexico and hike the prices charged in the U.S. (to cover the tariff), so they can wind up with the same bottom line.

Trump also wants to either reduce or eliminate the trade deficit with countries like Mexico and China. But there'll be nothing to stop them from raising their own tariffs on American goods. That's why they call it a trade "war" -- because both sides go on the attack. The trade deficit might actually widen as a result of tariffs.

The last big trade war the world saw was during the Great Depression. Economists argue about how much of America's Great Depression was caused by such legislation as the Smoot-Hawley Act, which levied the highest tariffs America had seen in the preceding century. It was signed into law in 1930, and then two years later (when the promised benefits, especially to farmers, failed to materialize) both Senator Reed Smoot and Representative Willis Hawley got booted out of office by their own constituents in the 1932 election. It was not a glowing success, in other words.

Since World War II, the world has been moving in the opposite direction, for the most part. The General Agreement on Tariffs and Trade (GATT) was signed in 1947, and later gave birth to the World Trade Organization (W.T.O.). These organizations became rather contentious in the late 1990s, in the midst of all the discussions surrounding the North American Free Trade Agreement (NAFTA), and awarding China "permanent most-favored-nation status." You may remember riots in the streets from GATT and W.T.O. meetings from 1999 (Seattle) onward.

Anti-trade sentiment now exists on both the left and the right, politically. This is one reason Donald Trump is now president, in fact. Trump badmouthed NAFTA and Obama's Trans-Pacific Partnership (T.P.P.) continually during the campaign, in a fashion not seen since H. Ross Perot (who famously predicted a "giant sucking sound" of jobs disappearing to Mexico if NAFTA passed). So Trump is now merely making a start on keeping his promises (such as pulling out and renegotiating NAFTA).

However, multinational macroeconomics isn't like building a skyscraper. It's in an entirely different ballpark. We may be about to see the results of such tinkering on a grand scale, in other words. Will Trump decide the Mexican tariff is working great and slap another big one on Chinese goods? That would put all our eggs in the tariff basket, that's for sure. Will the economists who predict doom and gloom be proven right, or is Trump smarter than them all? We may be about to find out.

Perhaps this is too alarmist, though. Donald Trump may either be constrained by the limits of his own presidential power, or he might just be playing a negotiating game. Of course, he could just be flying off the handle in a snit because the Mexican president just snubbed him by canceling their upcoming scheduled meeting. It's impossible to say, really.

Perhaps Trump is just playing hardball in an attempt to strike a favorable deal. If the Mexicans sit down at the table and renegotiate NAFTA so it gives America an advantage, then Trump won't have to slap a tariff on them and he can claim to all his followers that somewhere down in the fine print Mexico is actually paying for that wall! So maybe we'll have a few months of massive uncertainty but wind up (as Trump would say) "winning" in the end. Maybe.

Or perhaps Trump just hasn't realized that he can't actually make everything he wants happen merely by signing executive orders. He's now staked out positions that will either require congressional approval in some way or are just flat-out illegal under international law. Trump has recently been promising that he's going to see those two contentious pipelines get built -- with American steel. This would be a violation of W.T.O. rules, so it'll be interesting to see what Congress has to say about that. Congress will also have to appropriate all that taxpayer money to build the wall, as well as approve any brand-new border tax for Mexican imports. Trump can make pronouncements all he wants, but they don't always show results. For instance, on one of President Obama's first days in office, he signed an executive order to close down the prison camp at Guantanamo Bay, Cuba -- and it's still open to this day. Congress balked, and it never happened. Trump isn't king, in other words: Congress or the courts also get a say in most things.

Currently, trade is probably the biggest issue on which Trump and the Republicans in Congress seriously disagree upon. Republicans have traditionally been free-traders, for the most part. Having to debate a big tariff on Mexican imports is going to bring this rift out in the open, which is why it is doubtful American consumers will be paying one-fifth more for Mexican goods at any time in the near future. Democrats aren't exactly united on the issue either, as being against NAFTA and other big trade agreements is actually a subject that Trump and Bernie Sanders largely agree on. Progressives aren't happy with these agreements either, in other words. But progressives might not be as quick to support tariffs as the answer to fix the problems.

If Trump has his way and gets a big tariff on Mexican goods and then decides it's such a good idea that we do the same to China, we might all be headed to a trade war of truly nightmarish proportions. As I write this, the Mexican tariff news from the White House had just broken (nobody has had a chance to chime in on the plan yet, in other words). It will be interesting to see the reactions to it in the next few days. Was Trump just reacting to the Mexican president's snub? Will members of his own party (indeed, members of his own administration) be able to convince him to walk the threat back a bit? It all remains to be seen. I am no economist, macro- or otherwise, I will fully admit. I have no real concept of what the repercussions of a tariff on Mexican imports of 20 percent would be for the American economy. Few do, in fact. But we all may be about to find out which economists' predictions are correct and which are not.

-- Chris Weigant

Follow Chris on Twitter: @ChrisWeigant