Does overflying the US in low Earth orbit count as reentry? Or do you need to re-enter the atmosphere im order to re-enter?

Outer space is agreed upon by the USA as being beyond a country's sovereignty claims - https://www.unoosa.org/oosa/en/ourwork/spacelaw/treaties/int...

The Kármán Line is also generally accepted to be the boundary of outer space, set at 100 kilometers above ground.

The ISS orbits at something like 415km above Earth.

I'm no lawyer but is seems plausible to say no, orbiting above 100km of altitude over the USA would not be considered entry into the country.

You don't have to go through customs on every country you fly over in a regular plane. If I take off in California and fly to Hawaii I leave the airport like I never left the US, even though I've flown over "international" waters and have left the US' exclusive economic zone. I probably don't get a break if I'm in the air over Canada on the way to Alaska when it turns April 15th. If I take off from the US, orbit the earth a bunch on Tax Day, then land in the US was I "out of the country?" It _seems_ obvious but you did but you could potentially argue against it.

OTOH, if you leave US contiguous waters by boat and sit out in international waters for the month of April you have certainly left the country, even if you never entered another country.