Cigarette smuggling has a few aspects and each state while give it different priority based on its own economic incentives. But for a glimpse at the federal level, the ATF says [1] their justification is interested in enforcement (among other things) of:

"Illegal possession and/or transportation and distribution of more than 10,000 unstamped (non-state tax-paid) cigarettes."

This is mostly a tax revenue issue. Some other interesting info at the state level can be found at https://taxfoundation.org/data/all/state/cigarette-taxes-cig...

tldr; it will almost certainly take more than transporting "a few packs" for personal consumption to get in trouble in the "land of the free" at the federal level, however each state will he more or less aggressive depending on its own priorities

1. https://www.atf.gov/resource-center/fact-sheet/fact-sheet-to...