For a motor to be legal for use in the US, it must be certified by the EPA or exempt from EPA regulations. The 1VD is neither. Certification is a process prescribed by EPA that it's presumably only undertaken by manufacturers when they can justify the expense and hassle of it based on projected sales volume and other factors.
The details of how to EPA certify a motor are here:
Steps for certifying an onroad passenger vehicle with EPA.
www.epa.gov
The information linked above seems to be targeted at manufacturers, but I haven't dug deeply enough into it to ascertain whether the process could be undertaken by an individual or small business.
And, yes, the outcome would probably be preordained. That is, it would probably pass U.S. emissions standards.
Edit: I see that ICI's (Independent Commercial Importers) can probably do it. More info here:
Certification guidance and alternative fuel conversion information for manufacturers and independent commercial importers wanting to import vehicles and engines into the United States.
www.epa.gov
Again, I haven't dug into the weeds of this stuff, but it seems plausible, though likely prohibitively expensive.