Probably not, but reportedly a "White House insider" is afraid it might.
Instex is the new exchange created by UK, France, and Germany, to be based i Paris and run by a German banker, to get around US sanctions against Iran. Apparently it will sell Iran humaanitarian goods such as pharmacueticaals and food not subject to the sanctions, with those being paid for with Iranian petroleum that will then get sold elsewhere, none of this involving any US dollars. It is probably too small to threaten the dominance of the international SWIFT bank exchange system, but this does open up the possibility for nations to avoid US limits on their international financial transactions, with the US having used the SWIFT system in the past to crack down on unfavored nations.
There is a long, front page story in the Washington Post this morning about this matter Griff White and Erin Cunningham. For sstarters, I can relay that "Instex," which should probably be INSTEX, stands for "Instrument in Support of Trade Exchanges." Second is that the Trump'c campaign to get European, and especially German, companies to obey the anti-Iran US sanctions has beeen very agrressive and largly run out of the US Embassy in Berlin, with US Ambassador ro Germany, Richard Grenell, the point man on this. He had received press attention and criticism by some German business people when he arrived in Berlin last May and publicly called for German businesses to withdraw from Iran. That criticism did not slow him down one bit, and his efforts have led to some major German companies to withdraw, notably Siemans, VW, and Daimler-Benz, all of which have large-scale operations in the US.
But Grenell's efforts have gone far beyond that. People from his embassy have personally visited the HQs of many German companies, many of which have little connections with the US and much larger dealings with Iran, pressuring them in many ways, some friendlier, some involving threats and real actions. The most dramatic of the latter have come from the US apparently poressuinrg Deutsche Telekomm, which owns T-Mobile in the US, suddenly ending internet access and other telecom privileges for some of these compaines without warning, seriously disrupting their activities. Unsurpeisingly, this has drawn more sharp criticism from German business leaders.
What it does not seem to have drawn much of is open complaints from the German government, with Angela Merkel apparently for now trying to minimize conflicts with Trump, with there being so many issues at hand over which she and Trump differ.that she is sort of holding her fire for the biggest ones, and so far this stuff seems to be more an annoyance rather than super big, and with perhaps the strong German support for starting INSTEX sending the signal for now.
There is also the matter that Germany and several other of the major European powers are unhappy with Iran for apparently attempting to assassinate some of its own enemies from the MEK on Belgian and French soil last year, with several of those nations having institutes their own tightly focused sanctions on specific bodies in Iran identified with that effort. So there is a balancing act going on here, with Germany in particular opposing the US sanctiona and wanting to support the JCPOA backed by moderate Iranian President Rouhani, while themselves sanctioing hardline elements in the Iranian regime causing unwanted trouble in Europe.
I also note that in addition to UK, France, and Germany, the European Union is officially supporting the establishment of the INSTEX. For now it is a small operation not llikely to have too much effect on all this, but its potential for the future is another matter.