The EMP will be a nuclear weapons blast. It would be interesting to see if this was considered an act of war. If I had to decide, I'd say yes. Russia would be foolish to bring the wrath of the world on its head. However, Putin has not shown a great deal of sense or restraint in the war so far.
It is relatively easy to protect electronics against EMP. I know because I sold those products and did a fair bit of training on them. Military equipment is generally hardened to protect it. There will be a lot of disruption to commerce and industry.
So you would sit back and let China invade Taiwan? How about North Korea invade South Korea? While you're at it, throw Israel to the wolves. Let Iran have its nukes. Who are we to say psychos have no right to weapons of mass destruction?
If you are in a hurry to start WW3, you are on the right track. Sanctions have been somewhat effective in the past. If every tin pot dictator thinks he can invade another country for no reason, with no consequences, you can say goodby to modern civilisation.