Yes, we have not' bombed them because they are too big. But, we tried every other option. Pressurize them, sanction them. US Treasury even targeted the ships used for their trade, blocked insurance companies from insuring the route, targeted banks/people/entities for sanctions and did all sort of underground dirty work. Because of all this, the India-Iran oil deal is only intermittent, not continuous. There are windows of time where India/Iran are permitted to trade oil. Similar stories involving Russia. Their Stablecoin exchanges get hacked, people disappear. If you dig deeper, you will know more about SWIFT, Plaza Accord and other ways of how USA bullies the world.
Can you tell any smaller/weaker neighboring countries trading in their own local currency? Can Vietnam trade with Cambodia skipping the USD? not just for denominations, but the actual trade itself.