Sure, the standard could be made relatively easily, but how do you go about getting every bank to agree on this standard and update their systems to accommodate it, as well as the 10s of millions of POS terminals in the US alone to be updated, as well as all of the major credit card companies, etc.
You get banks to agree by mandating it. Just like the formats of SEPA Credit Transfers are written into law and required by all EU banks to support.
As for rollout: the NFC payment rollout took like a year to get to the point where I haven't encountered any non-NFC terminals since and that required all new hardware. Now that the hardware is out there, adding support for a new system is just a matter of software. At worst, a technician will have to visit every terminal and update the firmware manually (not sure if those things have OTA). "All the major credit card companies" == two, and it wouldn't really matter for their systems anyways since they're not banks, they are now-obsolete middlemen. People could still choose to use cards and vendors would likely still want to support them, there would simply be one more payment option available.
And yes, I agree that this would probably take forever in the US, but they're still using magstripe and the government is too big of a mess to be able to mandate a technical standard or even pass any legislation regarding banking anyways, so I think they have other things to deal with first.
