A 20 percent tax on Mexican imports will be disastrous for U.S. consumers, Rep. Jared Polis told CNBC Friday.

"The only thing that will come from this is devastation for both of our shared economies," Polis said on "Power Lunch."

Polis, a Democrat from Colorado, is not alone in his opinion. Other members of Congress believe the Trump administration's proposal to pay for a U.S.-Mexico border wall with tariffs will hurt American business.

"There's no reason, at all, to have a trade war or conflict with our close ally Mexico," Polis said. "And there are 4.9 million reasons not to — that's how many American jobs depend on trade with Mexico."

On Twitter, some users are using hashtags such as #AdiosStarbucks and #AdiosMcdDnalds in an effort to .

Polis said "ultra-nationalism is contagious" and that levying the proposed tariffs will encourage Mexico to levy their own.

"Frankly, if we engage in this kind of anti-competitive, anti-trade behavior, it will probably be the dollar that winds up suffering, as well."