Can somebody please help with this question?

Why did some states believe they had the power to overturn federal laws?

What misguided strategy caused lord william howe and the british to fail?

The picture below shows president richard nixon and the first lady standing before the great wall of china in 1972. they are smiling - as are the chinese with them. when this picture was shown on american television, americans were aware that it was a historic moment. what are two reasons why this moment was important for both china and the united states?