Based on the latest data from the U.S. Energy and Information Administration, Canada is far and away the largest single exporter @ just over 4M barrels a day. Russia is a significant individual exporter of crude oi to Americal, being 4th on the list (after Mexico @600K/d, Saudi Arabia @431K/d. Russia is just over 400K/d. From there it jumps down fairly significantly (200K/d.). https://worldpopulationreview.com/country-rankings/us-oil-imports-by-country
Not millions of barrels, but still a significant proportion of U.S. imports. Enough to consider upping imports per other countries or increasing domestic production. Of course that would also mean building an extra refinery or two. Which I believe we should do just for this exact reason... emergency production. If we can rattle on about being prepared with the grid in case of a freeze or significant weather event, we sure can say the same about war.
I believe Congress will succeed in getting us to stop buying Russian oil, at least I hope so. Given this situation, cutting their energy receipts goes far proportionately above mere percentages. At $40M or more per day, it should end - quickly.