The difference is deliberate and arbitrary attack of civilians at scale and total lack of concern - popularly, politically, operationally, and practically for casualties outside military targeting.
The notion one would even try to compare 'the Caribbean' - where USN is destroying drug running boats - which is arguably against some maritime laws but is nevertheless exceedingly acute, I think shows how wound up people are in the political context.
There is no relevant kinetic fallout in the Caribbean - it's an Elephant precisely stepping on a single ant.
Capture of Venezuelan Oil ... almost certainly illegal.
But that's a different thing
As for Vietnam - start by laying the context for why the N. Vietnamese imprisoned, tortured, killed 100's of thousands of political dissidents and civilians of all kinds, and continued that horrible repression for decades even to this day as they continue to crack down on mild dissent. The actual facts on both sides are actually ugly, but woefully misrepresented and the same utterly bizarre dual moral lens is applied ... a bit like in the Iranian situation as well.
Implied in the question is the despotism in plain site: why did N. Vietnam invade Cambodia? Against the will of those people? And murder and maraud in that territory?
The difference is between that, as a starting point, and strategic bombing of rural roadways (Ho Chi Min trail) etc., which ironically was in lieu of actually bombing North Vietnam which should have been done right from the onset, would have prevented a war, and saved 1/2 the population from a perennial nightmare and given the citizens some say in their future.
But it's also an example of the extent of the ability of superpowers to project power.