India's participation would be a question mark.
What we will likely see is a nuclear missile attack on the heart of the nation (Atlantic seaborad from New York City down to Washington, D.C.), from any of the following platforms: Cuba, Venezuela, the Russian Federation, Chinese submarine, or even space, contemporaneous with the disabling of our communication satellites, internet disablement, and television and radio jamming.
One should also expect strategic, surgical strikes against NORAD locations, missile silos, etc.
From Mexico, and internally, I could see the release of biological agents that their own soldiers would have been innoculated against.
Then I can see an incursion of more conventional forces (e.g., troops and tanks) landing in Florida (from their base in the Bahamas), and of course a massive incursion up and down the entirety of the West Coast.
The nuclear attack would also hinder any possible assistance from the European side, and depending on Canadian capabilities at the time, (I don't see Canada as much of a factor in the defense of the USA as an ally) but assuming some assistance could be expected there, perhaps the nuclear seal would be extended along that border.
(BTW, these are the capabilities that I see the PRC trying to develop; Currently, they wouldn't be able to carry this out).