I don't think realistically isolationism implies inaction. Let's suppose that it's the most "honest" cause. That is, attempting to prevent a Cuban Missile Crisis event by putting boots on the ground early. Then this doesn't contradict isolationism. In fact, I'd argue it's probably entirely within the bounds of "America First".
However, your point stands. Venezuela stands to benefit from an invasion because the country is unstable and teetering on collapse. It's essentially being sold to the highest bidder. If Russia/China want to put their boots there they will need to defend it and rebuild it. If the US wants to prevent Russia/China from doing that they will need to defend it and rebuild it. The US has far better global power projection and will likely spend considerable resources to ensure it's success as it's also, in some sense, a survival concern for the CONUS itself. I would think it could look a lot 1953 Iran, with the exception that power projection "down the street" (so to speak) is much easier to maintain than across the ocean.
However, your point stands. Venezuela stands to benefit from an invasion because the country is unstable and teetering on collapse. It's essentially being sold to the highest bidder. If Russia/China want to put their boots there they will need to defend it and rebuild it. If the US wants to prevent Russia/China from doing that they will need to defend it and rebuild it. The US has far better global power projection and will likely spend considerable resources to ensure it's success as it's also, in some sense, a survival concern for the CONUS itself. I would think it could look a lot 1953 Iran, with the exception that power projection "down the street" (so to speak) is much easier to maintain than across the ocean.