So, presidents can't control gas prices (or the general economy)?

Well, if "control" means fully control, that's true, and would even be true if the US were less federalist and more of a centralized national government, a la France. But, Macron also can't totally control the French economy. Setting aside acts of God, Xi Jinping might not 100 percent control the Chinese economy.

But, US presidents can influence the economy. And, they can influence oil prices, either directly influence oil prices, or influence the larger economy, which will then influence oil prices, and of course gas prices.

Take Shrub Bush 15 years ago. By 2006 or 2007, people who were educated news readers knew something about the housing bubble and why it was bubbly. Bush could have leaned on the Fed to start easing air out of that bubble, as well as leaning indirectly on the accreditation agencies to stop rating shit sandwich CDOs etc as being significantly above shit grade.

But, he didn't. And, no, I don't think he was totally idiotic about this. Yeah, he got gentleman's C's on his MBA, but he got an MBA.

That wouldn't have controlled the economy, but it would have influenced it. And, it would have influenced oil prices from not going to $147 a barrel (about $125-130 in today's terms). 

Or, before then, LBJ's guns and butter certainly influenced the economy. So did Nixon's price controls attempts.

As for influencing oil prices more directly?

Well, Russia IS the second-largest producer of oil after Saudi Arabia, and though it uses more itself, it's still a major exporter.

And, gee, WHY are oil prices so high right now?

Yes, recent winter storms were a factor, but as West Texas Intermediate threatens to approach triple digits, we all know the biggie: Russia and Ukraine.

And, those of us who aren't part of the bipartisan foreign policy establishment know the roots of all this: Slick Willie Clinton breaking Poppy Bush's promise not to expand NATO eastward. That then has been followed by hints, off and on for 15 years now, or more, that Ukraine (and Georgia, remember that?) would be covered by NATO's "umbrella" in some way. (Maybe we need Roe v Wade type penumbras and emanations?)

Then, there's "who's Ukraine?" Answer: kleptocrats and neo-Nazis. And, other than briefly, during the Russian Civil War, there's not been an independent Ukraine for centuries. Closest to that is the old Kievan Rus of pre-Mongol times.

From Biden's point of view, this is exacerbated by NATO members not wanting to fall fully in line on trade embargoing, and in some cases actively resisting. 

From the sensible point of view, the problems of NATO's European members are exacerbated by Biden, who may get lucky if Macron can get him off his tree limb.

Beyond backing off warmongering, there's other things Biden probably could do at the margins to help a smaller bit.

Could he knock prices back to $70 a barrel? Probably not any time soon. Could he ease them back to the $80/bbl range if he backed off on Ukraine and did whatever he could domestically on the edges?

Yes.

As for those gas prices? Panicky Democrats like Maggie Hassan and Mark Kelly wanting to nix the federal gas tax right now? This is a lower-grade version of the same dumb as suspending FICA taxes and other things. It's only 5 percent of the current cost of gas prices, and, since it hasn't been raised, well, since Slick Willie kneecapped Boris Yeltsin on NATO, it's part of why we needed Biden's infrastructure bill — our highways are crumbling.

And, Status Quo Joe's idea of releasing 50 million barrels of strategic reserve oil? We import 6 million barrels a day, and that is going up, slowly but surely, as the fracking miracle becomes hollow. Backing off warmongering would help a lot more. (We imported 10 million barrels a day in 2018.)