Great, then get them to stop buying oil from Putin.

Great. How? Hungary and Slovakia have refused to reduce their oil purchases. Their leaders are staunch supporters of Trump, and are well-regarded in the GOP base. That basically insulates them from any actual political pressure from the U.S., unless and until Trump is willing to take a bit of a political hit and actually go after them.

There's your 6%. China won't stop buying Putin's oil so that leaves India and Turkey.

India won't stop buying Putin's oil, so that leaves Turkey, Hungary, and Slovakia. Erdogan, Orban, and Fico.

The Europeans STILL buy enormous quantities of natural gas from the Russians. There's another place to look.

Already in process. The EU is taking up a complete ban on Russian gas imports. All imports under anything other than long-term contracts would be prohibited by this coming June; long-term contracts have until the following year.

The difficulty has been - and continues to be - Hungary and Slovakia. The EU doesn't have a single decision-maker that can impose their will on the collective. Sanctions require unanimous approval, so they haven't been able to pass these kinds of things over the fierce objections of two of the member-states. That's why Hungary and Slovakia were able to get an exception from the oil import ban - they were going to tank the whole thing if they weren't carved out. They've consistently threatened to do the same to a gas ban. This time, the EU thinks they've found procedural way around that - they're going to structure it as a change to the underlying energy regulations, rather than as a sanction. That allows them to bypass the unanimity requirement. The downside to that, though, is that Hungary and Slovakia will be outraged and likely tank any further effort to impose any economic sanction again, so this probably has to be the last one.

reuters.com - EU readies ban russian gas imports by end