>> The G7 group of advanced economies has reached a "historic" deal to make multinational companies pay more tax No, it hasn't. Some finance ministers met and talked: "Finance ministers meeting in London agreed to battle tax avoidance by making companies pay more in the countries where they do business. They also agreed in principle to a global minimum corporate tax rate of 15% to avoid countries undercutting each ot…
The executive is allowed to make executive agreements without consent of congress.
If you're thinking of the Iran nuclear deal, that's head-of-state stuff where the president is considered to have more powers (though of course it still was never a treaty, so could be/was scrapped easily by the next administration).