"We need to ally with Vietnam to stem the expansion of China in the region."
I agree 100%. Countries do not have permanent allies. They have permanent interests. Vietnam does not threaten our interests. China threatens our interests, and Vietnam's interests.
I understand, BTW, that the Vietnamese have some impressive Naval facilities in Cam Rahn Bay that could be pretty nice with a little refurbishment. Good RnR in Cap St. Jacques, too.
I have been to those impressive Naval facilities in Cam Rahn Bay after the USA built them.