"reached a deal" doesn't mean the deal absolutely 100% will be implemented. It means, the referenced parties have reached an agreement to something.

In this case, the leaders of the G7 countries have reached an agreement among themselves to have a minimum corporate tax rate. Note that the United States has no obligation according to this deal—only Joe Biden has agreed the deal. And Joe Biden has no legal obligation under the deal, he merely has a reputational one.

Since the agreed minimum corporate tax rate is 15%, and the United States corporate tax rate is 21% there's literally nothing Joe Biden needs to do in order to meet the terms of the deal he made with the other G7 leaders.

If they want to turn this into an international treaty, absolutely, GOP Senate votes will be needed (though, given that the treaty would create a floor that's 6 percentage points below our current tax rate, I would imagine those would be attainable votes—if the GOP created a global floor that was lower than our tax rate, they could use it to argue for lowering our corporate tax rate).