Maybe it does and maybe it doesn't but the fact remains it's overly simplistic to assume that plastic production doesn't temporally lead changes in health effects by some amount.

To suggest otherwise is clueless and asinine.

does the US consume a lot more plastic than elsewhere?

Probably. But frankly I don't care, because that's irrelevant. Plastic pollution is global.

in which case it doesn't explain why America specifically has a lowered life expectancy.

It's almost like life expectancies cannot be explained by a single variable, and the original claim that life expectancies went up thus plastics aren't bad is overly simplistic. Imagine that.