Americans, how often and casually do you cross a State line?

State lines are pretty much irrelevant. They're markers of authority — this state is responsible for stuff on this side of the imaginary line, and that state is responsible for stuff on that side. For the most part, no one cares.

Whenever we want or need to.

very often and very casually

It's no big deal to cross a state line... if they didn't have big signs that say "welcome to ...." you wouldn't even notice it most of the time .

Some cities are even in two different states. People live in one state and work in another.

It's no big deal, except in rare occasions it is just a sign you pass before seeing the police in different cars... Of course going into California, you have to verify you're not taking fresh fruit into the state.

There are no states in the UK.

We live a mile from the border with the Irish Republic so do it nearly every day. Probably won't change with Brexit.

you're talking about different countries (even if they all form the UK), that's not quite the same as crossing States

State line. I thought England. Wales Ireland and Scotland were countries.?. All little countries. My Dad everyday.

we got Provinces but i hardly even go downtown never mind another province

Why do you avoid crossing boundary lines---inside of the same country??

My dad crosses it everyday. He lives in one state but works in another.

The New England states are so small, it's hard to notice sometimes.

I cross through (4) everyday with my commute. Kind of cool I guess..