Co2 tax is just an indirect subsidy for renewables. When prices are low those are subsidized through cfds. When high- through merit order artificially pumped by co2 tax. This isn't bad per se but it affects negatively final consumer prices and industry which is bad.

Problem is not about the neighbors throwing trash. Unilateral co2 tax means industry relocates to regions where it's not present. In your analogy it would look like you are sending trash to US to deal with it.

DK is lucky to be able to get firming from nordics, but not everyone can do this. And from what I remember Norway already said one of the interconnectors will not have extended license at EOL