The Penn State Extension is a taxpayer-funded horticulture service for PA residents (Penn State operates it on behalf of the state).

Here is their page on getting rid of Tree Of Heaven: https://extension.psu.edu/tree-of-heaven-control-strategies. They also have a summary page with an extensive section on controlling it: https://extension.psu.edu/tree-of-heaven.

tldr: Cutting it down will not work. Like others mentioned, you need to apply the right types of herbicide at just the right time to be effective (mid-summer until the leaves start to turn). If you applied herbicide after the leaves turned, it probably didn't work and you'll have to try again around August.

Penn State Extension operates per-county hotlines. Heres the one for Allegheny County: https://extension.psu.edu/programs/master-gardener/counties/allegheny/hotline.

They are *very* interested in reducing Tree Of Heaven because it is the main vector for Spotted Lanternflies.